Transducer for fm sonar application

Claim 2

An electroacoustic transducer comprising: first and second pairs of piezoelectric elements; said piezoelectric elements of said first pair being substantially semi-disc shaped and presenting flat front surfaces each bounded by a straight side surface and an arcuate side surface, said piezoelectric elements of said first pair being disposed with said front surfaces in a first common plane with said straight side surfaces in adjacent, spaced, parallel relation to one another and said arcuate surfaces lying in a circle; said piezoelectric elements of said second pair being substantially semi-annular in shape and presenting flat front surfaces each bounded by inner and outer arcuate surfaces and straight end surfaces, said piezoelectric elements of said pair being disposed in concentric relation to said first pair with said front surfaces lying in said first common plane and said inner arcuate surfaces in uniformly spaced relation to said arcuate surfaces of said piezoelectric elements of said first pair, said straight end surfaces being in spaced parallel relation to one another; said piezoelectric elements of said first and second pairs being further characterized by flat rear surfaces lying in a second common plane; front electrode means, on each of said front surfaces, for effecting electrical connection therewith; rear electrode means, on said rear surfaces, for effecting electrical connection therewith; and said piezoelectric elements each being further characterized by a plurality of intersecting slots formed in said rear surfaces and defining a plurality of rearwardly extending posts on each of said piezoelectric elements.

Claim 3

An electroacoustic transducer as defined in claim 1, and wherein: said rear electrode means comprises a metal mesh soldered to said rear surfaces at the end of each of said posts.

Claim 4

An electroacoustic transducer as defined in claim 2, and further comprising: acoustic energy barrier material disposed between said straight side surfaces of said piezoelectric elements of said first pair, between said end surfaces of said piezoelectric elements of said second pair, and concentrically between said first and second pairs of piezoelectric elements.

Claim 5

An electroacoustic transducer as defined in claim 3, and further comprising: a layer of acoustic barrier material disposed in encircling engagement with said outer arcuate surfaces of said piezoelectric elements of said second pair.

Claim 6

An electroacoustic transducer as defined in claim 4, and further comprising: a disc-shaped layer of said acoustic energy barrier means disposed against said rear electrode means in covering relation to said first and second pairs of piezoelectric elements.

Claim 7

An electroacoustic transducer as defined in claim 5, and wherein: said spaced end surfaces of said second pair of piezoelectric elements are aligned with said straight side surfaces of said first pair of piezoelectric elements.

Claim 8

An electroacoustic transducer aS defined in claim 6, and further comprising: electrically insulating and waterproof acoustic window means, overlying said front surfaces of said first and second pairs of piezoelectric elements and said acoustic barrier material therebetween, for effecting acoustic coupling between said front surfaces and an ambient water medium.

Claim 9

An electroacoustic transducer as defined in claim 7, and wherein: said acoustic window means comprises a layer of substantially acoustically transparent deaerated polyurethane material.

Claim 10

An electroacoustic transducer as defined in claim 8, and wherein: said acoustic window means further comprises a layer of substantially acoustically transparent rubber-like material.

Claim 11

An electroacoustic transducer for simultaneous projection and reception of acoustic energy into and from an aqueous medium with minimized cross-coupling, said transducer comprising: a pair of substantially semi-disc shaped, piezoelectric projecting elements having arcuate side surfaces arranged on a first circle and straight side surfaces in parallel, spaced relation, said projecting elements being polarized for thickness excitation between front and rear surfaces thereof; a pair of substantially semi-annular shaped, piezoelectric receiving elements having inner and outer arcuate side surfaces respectively arranged on second and third circles concentric with said first circle and straight end surfaces disposed in spaced parallel relation to one another, said receiving elements being polarized for thickness excitation between front and rear surfaces thereof; acoustic energy absorbing material disposed between said straight side surfaces of said projecting elements, between said straight end surfaces of said receiving elements, and between said arcuate side surfaces of said projecting elements and said inner arcuate side surfaces of said receiving elements; said projecting and receiving elements being characterized by intersecting grooves formed in said rear surfaces and extending through a majority of the thickness of said elements so as to define a plurality of rearwardly extending, discrete posts and so as to interrupt planar vibration transmission within each of said elements; front electrode means comprising a layer of electrically conductive material on said front surfaces of each of said piezoelectric elements; rear electrode means comprising electrically conductive wire mesh overlying said rear surfaces and electrically bonded thereto, said wire mesh being loosely woven so as to be substantially free of vibratory energy transmission from point to point thereof; a layer of acoustic energy absorbing material disposed behind said wire mesh in loosely coupled engagement therewith; a layer of acoustic energy absorbing material in encircling relation to said first and second piezoelectric elements; a layer of substantially acoustically clear deaerated polyurethane compound encapsulating said projecting and receiving elements, said electrode means, and said acoustic energy absorbing material; and conductor means, connected to said electrode means, for applying energizing electrical signals to said projecting elements and for collecting electrical signals from said receiving elements.

Claim 12

An electroacoustic transducer for simultaneous projection and reception of acoustic energy into and from an aqueous medium with minimized cross-coupling, said transducer comprising: a pair of substantially semi-disc shaped, piezoelectric projecting elements having arcuate side surfaces arranged on a first circle and straight side surfaces in parallel, spaced relation, said projecting elements being polarized for thickness excitation between front and rear surfaces thereof; a pair of substantially semi-annular shaped, piezoelectric receiving elements having inner and outer arcuate side surfaces respectively arranged on second and third circles concentric with said first circle and straight end surfaces disposed in spaced parallel relation to one another, said receiving elements being polarized for thickness excitation between front and rear surfaces thereof; acoustic energy absorbing material disposed between said straight side surfaces of said projecting elements, between said straight end surfaces of said receiving elements, and between said arcuate side surfaces of said projecting elements and said inner arcuate side surfaces of said receiving elements; said projecting and receiving elements being characterized by intersecting grooves formed in said rear surfaces and extending through a majority of the thickness of said elements so as to define a plurality of rearwardly extending, discrete posts and so as to interrupt planar vibration transmission within each of said elements; front electrode means comprising a layer of electrically conductive material on said front surfaces of each of said piezoelectric elements; rear electrode means comprising electrically conductive wire mesh overlying said rear surfaces and electrically bonded thereto, said wire mesh being loosely woven so as to be substantially free of vibratory energy transmission from point to point thereof; a layer of acoustic energy absorbing material disposed behind said wire mesh in loosely coupled engagement therewith; a layer of acoustic energy absorbing material in encircling relation to said first and second piezoelectric elements; a layer of substantially acoustically clear deaerated polyurethane compound encapsulating said projecting and receiving elements, said electrode means, and said acoustic energy absorbing material; and conductor means, connected to said electrode means, for applying energizing electrical signals to said projecting elements and for collecting electrical signals from said receiving elements.

Claim 13

An electroacoustic transducer as defined in claim 10, and wherein: said straight side surfaces of said projecting elements are in alignment with said straight end surfaces of said receiving elements.