Communications – electrical: acoustic wave systems and devices – Seismic prospecting – Offshore prospecting
Patent
1983-04-08
1985-01-01
Wilbur, Maynard R.
Communications, electrical: acoustic wave systems and devices
Seismic prospecting
Offshore prospecting
367154, 367166, 1741015, 174108, G01V 138
Patent
active
044919395
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a hydrophone cable and in particular it relates to certain improvements to cables of this type which are towed in the ocean and which are arranged as acoustic arrays comprising a series of hydrophones spaced at required intervals and carried in a buoyancy device to allow towing from a vessel at a required depth below the surface of the ocean.
Such devices are used for seismic exploration and for ship and submarine detection and similar purposes and operate on the basis that the hydrophones are coupled either singly or in groups to instrumentation on board the vessel to act as sonar detectors.
The arrangement of these devices as known at present is such that neutral buoyancy is achieved and according to forms of the device at present in use the hydrophones are spaced along a towing cable with which are also associated the transmission lines which transmit the signals from the hydrophone to the vessel. The transmission lines (for data and power), hydrophones and other components (preamplifiers, other sensors, spacers etc.) are contained in tubular pliable devices (casings or sleeves) which are filled with a buoyant fluid such as kerosene so that neutral buoyancy is achieved of the complete assembly. The configuration is such that the required sensitivity of the hydrophones is not lost because of their enclosure in the casing, the buoyant fluid fill having the required acoustic properties to transmit the sound pressure waves from the casing wall to the hydrophone elements.
Typical Prior Art Specifications are; U.S. Pat. No. 3,480,907 J. D. King which shows a hydrophone cable having hydrophones along its length at spaced intervals and including a jacket with tensile members along the inside of the outer sheath and teaching generally the art of neutral buoyancy, also U.S. Pat. No. 3,696,329 G. D. Hazelhurst, U.S. Pat. No. 3,518,677 E. F. Florian, U.S. Pat. No. 3,434,104 F. E. Stapleton et al, U.S. Pat. No. 3,319,734 G. M. Pavey, JR., U.S. Pat. No. 3,371,311 J. Colet et al, U.S. Pat. No. 3,531,760 W. A. Whitfill, JR., U.S. Pat. No. 3,744,016 B. W. Davis, U.S. Pat. No. 3,978,446 G. Kirby Miller, and Australian Pat. No. 457,052 Whitehall Electronics Corporation.
In the above hydrophone cables are shown having generally the characteristic of streaming cables which are generally of neutral buoyancy, but thecost of such devices is relatively high and intricate and handling is a problem because of the long lengths usually involved and the bulk of the units coupled with the need to be able to store the device on a vessel when not in use.
It is the object of this invention therefore to provide an improved form of acoustic array which will not have the intricacy of the previously used devices but which will be effective in picking up sounds and will be as free as possible of noise normally caused through turbulence of the water around the array during towing.
The device according to this invention consists of a cable-like structure constructed of polypropylene and/or similar materials which together have the required buoyancy and tensile strength, and with which are incorporated the spaced hydrophones and the leads for transmitting the signal from the hydrophones along the array to the vessel, the cable of this invention being of braided construction such as by using a core of polypropylene or of the material known under the trade name of "KEVLAR" and to wind around this in helical form the transmission cables which can be wound in a matrix of the buoyant material, a sheath being extruded or otherwise placed over the whole assembly including the hydrophones which hydrophones can conveniently be of elongated form to fit into the cable, but the construction can be varied to have the high tensile members outwards of a core.
Because the structure can be built up of fibres forming cords wound into a particular pattern it will be realised that for instance a series of hydrophones can be spaced at required distances apart by untwisting the polypropylene core at the area where they are to be inserted so
REFERENCES:
patent: 3659256 (1972-04-01), Hudson et al.
patent: 4160229 (1979-07-01), McGough
patent: 4241427 (1980-12-01), Swenson
patent: 4353120 (1982-10-01), Pickens
Lobo Ian
The Commonwealth of Australia
Wilbur Maynard R.
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