Abstract: Various sensors use an electro-active device (11) electrically connected to a detector circuit. The electro-active device (11) comprises an electro-active structure in the form of a continuous electro-active member (12) curving in a helix around a minor axis (13) which is in itself curved for example in a helix around a major axis (14). On activation by relative displacement of the ends (16) of the device (11), the electro-active structure twists around the minor axis due to the fact that the minor axis (13) is curved. The continuous member (12) has a bender construction of a plurality of layers (21) and (22) including at least one layer of electro-active material so that concomitantly with the twisting the continuous member (12) bends generating an electrical signal detected by the detector circuit. The electro-active device (11) is advantageous as a sensing element in a sensor because it has a large displacement, high sensitivity and low compliance.

Abstract: The invention is directed towards structures for use with micro-formed membrane ultrasonic transducers, and methods for fabricating the structures. In one embodiment, the transducer includes a planar member having a piezoelectric material and spaced apart electrodes disposed on the planar member and coupled to the piezoelectric material for applying an electric field to the layer, and an acoustic backing member joined to the electrodes. In another embodiment, the transducer includes a planar member having a piezoelectric material that adjoins a semiconductor material, the semiconductor material having monolithically formed active circuits formed in the layer and coupled to the piezoelectric material. In still another embodiment, the transducer includes a planar member having a piezoelectric material, and an acoustic backing member having an adjoining layer of a semiconductor material having monolithically formed active circuits, the active circuits being coupled to the electrodes.

Abstract: An improved transducer arrangement for low frequency sonar projectors that convert electric signals to mechanically generated acoustic signals. In one embodiment the arrangement has both a convex flextensional transducer and a concave flextensional transducer. An open side of the convex transducer is attached to an open side of the concave transducer by an intermediate bulkhead which closes each of the attached open sides. An end plate is attached to another open side of the convex transducer and another end plate is attached to another open side of the concave transducer such that the end plates close the attached open sides. In another embodiment, transducer assembly has a convex transducer having end plates and a concave transducer having end plates. Either one of the endplates of the concave transducer is attached to one of the endplates of the convex transducer, or an endplate of the concave transducer is also an endplate of the concave transducer.

Abstract: An improved transducer arrangement for low frequency sonar projectors that convert electric signals to mechanically generated acoustic signals. In one embodiment the arrangement has both a convex flextensional transducer and a concave flextensional transducer. An open side of the convex transducer is attached to an open side of the concave transducer by an intermediate bulkhead which closes each of the attached open sides. An end plate is attached to another open side of the convex transducer and another end plate is attached to another open side of the concave transducer such that the end plates close the attached open sides. In another embodiment, transducer assembly has a convex transducer having end plates and a concave transducer having end plates. Either one of the endplates of the concave transducer is attached to one of the endplates of the convex transducer, or an endplate of the concave transducer is also an endplate of the concave transducer.

Abstract: There is provided an acoustic source especially for use in seismic studies at sea. The acoustic source has a longitudinal axis and sound emitting surfaces adapted to be put into sound emitting movements towards and away from each other by use of a drive unit. The sound emitting surfaces comprise two curved plate members having upper and lower ends essentially symmetrically positioned in relation to the longitudinal axis of the acoustic source, and forming a convex cross section with their respective upper and lower edges converging towards each other. The upper and lower edges of the sound emitting surfaces, respectively, are connected to each other with two corresponding side elements, the side elements each being connected to at least one hinge stretching along at least a part of the length of the source.

Abstract: The present invention relates to an underwater acoustic projector compris a housing formed from a rigid material, a fixed plate secured to the housing, a first annular electrostrictive ring and a second annular electrostrictive ring positioned on one side of the fixed plate, and a third annular electrostrictive ring and a fourth annular electrostrictive ring positioned on a second side of the fixed plate. The first and second annular rings are separated by a first moving plate, while the third and fourth annular rings are separated by a second moving plate. The annular rings are formed from lead magnesium niobate or lead magnesium niobate-lead titanate and are wired for dual push-pull operation for reducing the non-linearity of the response of the annular rings.

Abstract: The present invention relates to an underwater acoustic projector compris a housing formed from a rigid material, a fixed plate secured to the housing, first and second annular electrostrictive rings positioned on one side of the fixed plate, and third and fourth annular electrostrictive rings positioned on a second side of the fixed plate. The first and second annular rings are separated by a first moving plate, while the third and fourth annular rings are separated by a second moving plate. Each moving plate is connected to a drive piston which contacts an inner surface of an outer housing surrounding the inner housing. The outer housing is caused to move in a flexural mode by the drive pistons in contact with it. The annular rings are formed from lead magnesium niobate or lead magnesium niobate-lead titanate and are wired for dual push-pull operation to reduce the non-linearity of the response of the annular rings.

Abstract: The piezoelectric-acoustic transducer of the present invention has a hollow case provided with a sound hole. A piezoelectric actuator is disposed inside this case that has one end fixed to the case and that bends in the direction of the thickness of the case when voltage is applied. A diaphragm is secured to one portion of the piezoelectric actuator and is positioned at a distance from the piezoelectric acturator in the direction of the thickness of the case.

Abstract: A composite sensor includes at least one layer comprising a piezoelectric material such as a molecularly poled polymer material or a ceramic material having disposed therebetween a material which enhances the piezoelectric properties of the piezoelectric material. One pair of edges of said composite sensor are constrained from expanding in response to a force applied to the sensor.

Abstract: This invention describes an acoustic transducer assembly wherein an extremely high figure of merit (d.sub.h g.sub.h) is obtained as a result of converting incoming acoustic axial stress into radial extensional stress thereby multiplying its effect. The piezoelectric active element is encased in a metal sandwich enclosing two semilunar air spaces which allow the device to withstand extremely high hydrostatic pressure yet still respond to low level sound waves when acting as a hydrophone. The mechanical prestress induced by the differential coefficients of expansion between the metal case and the piezoelectric ceramic element also serves to prevent depolarization aging.

Abstract: A cylindrical shell enclosure has mounted interiorly thereof in cantilever manner four upstanding laminated planar flexible resilient electroacoustic transducer reeds. A separate inertia weight is affixed to the top edge of each reed. An acoustic wave impinging on the side wall of the submerged enclosure will cause relative movement between the enclosure and a weight if the wave direction has a component transverse to the plane of the reed on which the weight is mounted. The reeds are mounted in quadrature so that wave direction detection is provided by comparing the electrical outputs of the reeds. Viscoelastic damping pads may be affixed between the side ends of each of the weights and respective upstanding rigid arms secured to an interior surface of the enclosure.

Abstract: A directional velocity hydrophone is provided which does not appreciably disturb the particular movement of the fluid in which it is plunged and which comprises bending blades disposed in a ring and embedded in an inertial mass, which deliver an electric current substantially proportional to the particular speed of the fluid.

Abstract: A single element cantilever mounted shear wave transducer which takes advantage of the transverse vibration of a piezoceramic bimorph element mounted as a cantilever on a heavy slug. A gasket material between the slug and an inner holding tube assists in avoiding the propagation of undesirable compressional wave energy into transmission medium surrounding the transducer. Electrical isolation is achieved by wrapping the inner tube with a ground shield to which the ground wire is attached. A second layer of gasket material between the inner and an outer tube further inhibits the propagation of compressional wave energy into the transmission medium. A flexible potting compound seals the open end of the tubes including the bimorph element and serves as the active face of the transducer.

Abstract: Probe method and means are disclosed for guiding and positioning a robot-actuated tool, such as a gripper or a welding head, through at least one transceiver for generating and sensing focused shockwaves, the probe being associated with the tool for relative movement with respect to the object or objects being sensed, without physically contacting the same.