Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-05-03
2001-10-30
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S334000, C310S369000, C367S165000
Reexamination Certificate
active
06310427
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of acoustics and, in particular, to configurations of electrical connectors for electro-acoustic devices.
BACKGROUND OF THE INVENTION
An important feature of any acoustic system is the transducer. A transducer typically incorporates an electro-acoustic element which converts electrical signals into mechanical vibrations in the transmit mode and mechanical vibrations into electrical signals in the receive mode. There are many factors that influence the behavior of a transducer, including the choice of material, physical dimensions, electrical connection, mechanical construction, the external load conditions and the capacity to dissipate heat.
Ceramic cylinders frequently constitute the electro-acoustic element in underwater acoustic transducers and may be either tangentially poled or radially poled. Tangentially poled cylinders provide higher electro-mechanical coupling than radially poled cylinders, making them the preferred choice for many high-power, broadband applications. Tangentially poled cylinders have striped electrodes and operate in the k33 mode (i.e. the direction of the electric field is the same as the direction of the dielectric displacement). Radially poled cylinders have an electrically conductive plating on the outer and inner surfaces and operate in the k31 mode (i.e. the direction of the electric field is orthogonal to the direction of the dielectric displacement).
One particularly common problem with transducer construction is the difficulty of creating a reliable method of making the electrical connection to the electrodes. The conventional way of connecting to the electrodes on ceramic is to use soldered wire. On tangentially poled cylinders this entails soldering daisy-chained wire to alternate striped electrodes while on radially poled cylinders, wire is soldered to the inner and outer surfaces.
One of the problems with this method is that the solder joint is an unreliable connection, subject to failure during either handling or actual operation. This inherent unreliability of the solder joint originates in the soldering process. When solder is applied to one end of a wire, expansion occurs. Then the solder solidifies and as the wire cools it contracts. If additional wire length is not left to compensate for the heating and subsequent cooling, the wire will stretch and generate stress in both the wire and the solder joint. In small tangentially poled ceramic cylinders, the close proximity of the solder connections makes it difficult to leave adequate wire length in the daisy chain to relieve the process-induced stress.
Besides being unreliable, the soldering process is also labor intensive. This is especially true in tangentially poled cylinders with a large number of striped electrodes.
Additional problems with the solder connections occur in high frequency, high power applications. The large acceleration force on the solder joint causes the wire to flex. This can result in mechanical fatigue and wire fracture. The fractured joint could then induce arcing, resulting in catastrophic failure.
Therefore, there is a need for an approach which controls wire flexing in ceramic cylinders using solder joints or eliminates the need for soldering wires to the ceramic altogether. There is also a need for a standardized process that reduces human intervention in transducer manufacture. In addition, there is a need to provide design simplicity, reliability, and reduced labor costs along with improved heat transfer from the ceramic cylinders.
SUMMARY OF THE INVENTION
The present invention presents modified configurations of electrical connectors for an electro-acoustic transducer. One modification replaces the daisy chain configuration on tangentially poled cylinders with a pin configuration that controls the geometry of the soldered wires. The soldered end of each wire runs parallel to the stripe and the other end is substantially perpendicular to the interior of the ceramic cylinder. This prevents tensile forces from acting on the electrical connectors and distributes the flexing over a longer length of wire.
A preferred embodiment of the invention is a plug connector for a tangentially poled cylinder. The plug connector replaces the mechanical solder bond with a contact that relies on pressure to control the conductance. In its most basic form, the plug connector consists of a series of contact carriers that are aligned with the striped electrodes on the ceramic cylinder. Metal electrical contacts are inserted into the carriers and are linked together on an alternating basis to form positive and negative electrical connections. The ceramic cylinder slides onto the plug connector to form an assembled condition where the electrical connection to the ceramic cylinder is achieved through physical contact. This construction forms a basic ceramic cylinder transducer using a plug connector that can be modified depending on the application of the assembly.
The plug connector, by utilizing edge contacts similar to those used in a PC board, provides the electrical connection to the striped electrodes on the ceramic cylinder and eliminates the need to solder to the ceramic. Design simplicity and improved heat transfer are other potential benefits. These are apparent when the material for the plug connector is both electrically and thermally conductive. Use of an electrical conductor eliminates the need to physically connect each contact, and use of a thermal conductor helps dissipate heat from the ceramic.
A preferred embodiment of the plug connector is a construction where the negative contact carriers are incorporated into the metallic structure or foundation that secures the cylindrical transducer. By connecting the structure to the ground of the power amplifier, all of the contact carriers, contacts and negative electrodes are properly grounded. In a similar way, connection to the positive contacts can be simplified by mounting them in a single metallic contact carrier that is properly insulated from ground. By connecting the metallic contact carrier (which resembles a spider, with one leg for each positive contact) to the output of the power amplifier, all of the positive electrodes are properly connected. Thus only two connections, one to the positive spider and the other to the negative foundation, are required to power a plurality of electrodes on the ceramic. This substantially reduces labor costs and improves reliability. Improved heat transfer is achieved by exposing the foundation to surrounding water, thus providing an effective heat path to dissipate heat from the ceramic.
Therefore, it is an aspect of this invention to provide electrical connectors that reduce tensile forces from acting on the connectors during transducer operation.
It is another aspect of the invention to provide electrical connection to striped electrodes on tangentially poled ceramic cylinders through pressure from an electrical contact rather than by soldering wires to striped electrodes.
It is another aspect of the invention to provide electrical connection to the inner surface of a radially poled cylinder through pressure from an electrical contact rather than by soldering a wire to the ceramic.
It is a further aspect of the invention to provide a simple, reliable, and cost effective means of making electrical connections to ceramic cylinder transducers.
It is a further aspect of the invention to provide a modified plug connector of electrically and thermally conductive material for use in ceramic cylinder transducers.
REFERENCES:
patent: 3142035 (1964-07-01), Harris
patent: 4525645 (1985-06-01), Shirley et al.
patent: 4827459 (1989-05-01), Franklin
patent: 5130953 (1992-07-01), Grosso
patent: 5694374 (1997-12-01), Ripoll et al.
Culbert James A.
Dexter, II William H.
Dickie Warren J.
Guida Edward
Longabard Anthony
BAE SYSTEMS Aerospace Inc.
Budd Mark O.
Onders Edwards A.
Ritchie William B.
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