Communications – electrical: acoustic wave systems and devices – Signal transducers – Underwater type
Patent
1988-09-14
1989-08-29
Steinberger, Brian S.
Communications, electrical: acoustic wave systems and devices
Signal transducers
Underwater type
367158, 367162, 310337, H04R 1700
Patent
active
048624284
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a distributed array hydrophone and in particular it relates to a hydrophone which may be mounted on a submarine or the like for the purpose of receiving underwater signals.
This type of device is a passive array consisting of a number of individual hydrophone elements positioned at predetermined distances from each other and connected electrically in either series or parallel or a combination of series-parallel arrangements.
According to the system generally used on, for instance, submarines the arrays consisted of single elements connected by a flexible cable. This resulted in reliability problems when a cable entered and exited the hydrophone elements. The construction of the element itself was complicated as was the encapsulation process which involved the moulding of butyl rubber, and the outer tube required to have a series of polyethylene joins.
An improvement to this design was to have radially-poled ceramic tubes positioned at predetermined intervals along a stainless steel rod, the assembly being pre-stressed and followed by encapsulation in polyethylene using injection moulding techniques.
During development work it was found that the stiffness of a structure of this general type caused mechanical resonance within the stave which was within the required operating range of frequencies and attempts to decouple the ceramic from the structure proved unsuccessful. The object of this invention therefore is to provide a general assembly of this type but of a more successful nature free of the coupling referred to, in which assembly resonance problems are overcome by the design and in which greater effectiveness of the unit is attainable.
The design of this invention consists of individual ceramic elements which are fitted with end plates and these plates are decoupled from the ceramic by pressure release material, the element assemblies being connected together by using semiflexible spacers which accurately set the spacing of the elements and also house the wiring which connect the elements electrically, this sub-assembly being loaded into an extruded polyethylene or similar tube which has moulded to it an end cap and mounting feet and the elements are then encapsulated in a potting medium such as polyurethane.
To enable the invention to be fully appreciated reference may be had to the accompanying drawings in which,
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates in longitudinal section a ceramic doublet assembly,
FIG. 2 is a sectional elevation of the hydrophone sub assembly embodying the ceramic doublet assemblies and,
FIG. 3 is a sectional elevation of the complete array.
Referring first to FIG. 1, it will be seen that the ceramic doublet assembly 1 comprises a pair of ceramic members 2-3 of tubular form which are radially oppositely polarized and held in a rigid bobbin 4 by interposed decoupling member 5 between end flanges 6-7 of the bobbin 4 and the ends of the ceramic doublet assembly 1, the signal being taken from the junction portion of the doublet assembly through an axial hollow 8 in the bobbin 4 or in any other means. The bobbin 4 is in two parts held together by a hollow retaining screw 9.
A plurality of such ceramic doublet assemblies 1 are spaced apart by interposed sections of semiflexible tube 10 which can also carry the electrical leads 11 so that an assembly of accurately spaced hydrophones results in which the ceramic doublet assemblies 1 are free of end pressure in the bobbin 4 and can therefore be enerized by vibration applied to the external surface 12 while the signal is collected at the junction 13 from the internal surface 14. A conductor 15 bridges the junction 13, the ceramic members 2-3 being bonded together at the junction 13.
After forming such a hydrophone sub assembly, the assembly as shown in FIG. 2 is positioned in an outer pressure wave transmitting tube 16, as shown in FIG. 3 resilient spacing members 17 being used where required, and the tube 16 is filled with potting medium 18 such as polyurethane so that the ceramic doublet assem
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patent: 4017824 (1977-04-01), Fife et al.
patent: 4160229 (1979-07-01), McGough
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patent: 4208738 (1980-06-01), Lamborn
patent: 4733379 (1988-03-01), Lopetina et al.
patent: 4766575 (1988-08-01), Ehrlich et al.
Jackett Stephen G.
Jandera Zdenek
Kastel Stephen N.
Plessey Australia Pty. Limited
Steinberger Brian S.
The Commonwealth of Australia
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