WO1989008270A1

WO1989008270A1 - Improvements in or relating to arrays of filamentary form

Info

Publication number: WO1989008270A1
Application number: PCT/GB1989/000186
Authority: WO
Inventors: Roy Wyatt
Original assignee: Roy Wyatt
Priority date: 1988-02-24
Filing date: 1989-02-23
Publication date: 1989-09-08
Also published as: EP0409863A1; GB2215461B; GB2215461A; AU3355189A; GB8804314D0

Abstract

An array (1) of filamentary form comprises a cylindrical body (10) housing a centrally-disposed reinforcement member (11) and a plurality of sound-wave sensors (12) distributed within the body (10), in the proximity of the external surface (13) of the body (10). The array (1), which is suitable for geophysical survey purposes, may be towed through water (2) by a vessel (3). The reinforcement member (11) is used to accept towing loads applied to the array (1), to serve as a databus for conveying signals emitted by the sensors, and to conduct electrical power to the sensors (12).

Description

"Improvements in or relating to Arrays of filamentary Form"

BACKGROUND TO THE INVENTION

This invention relates to arrays of filamantary form.

The invention is particularly but not exclusively concerned with towable arrays whereby water-bome sound waves generated for geophysical survey purposes may be sensed. OBJECT OF THE INVENTION

One object of the invention is to provide an array of filamentary form which is of substantially IBSS lateral cross-section than presently known arrays. SUMMARY OF THE INVENTION

According to the invention, an array of filamentary form comprises a body housing a central, longitudinally-extending reinforcement member and a plurality of sensors distributed within the body of the array, in the proximity of the outer surface thereof,wherein said centrally-disposed reinforcement member serves to convey signals emitted by the sensors.

The centrally-disposed reinforcement member may also serve to conduct electrical power to the sensors.

For towing through water, the central member may be formed and constructed 90 as to accept towing loads applied to the array. BRIEF DESCRIPTION OF THE ACCODPANYING DRAWINGS

An embodiment of the invention mill now be described by way of example only, with reference to the accompanying drawings, wherein :- Figure 1 illustrates the towing of a sound-wave sensing array through water,

Figure 2 is a fragmentary side view, in medial section, of the array, and Figure 3 is a view similar to that illustrated by Figure 2 and shows a modification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference first to Figure 1, a water-borne sound-wave sensing array 1 of filamentary form is shown being towed through water 2 by a marine craft comprising a surface vessel 3. The array 1 is towed through the water for geophysical survey purposes, being used to sense sound waves resulting from applying shock loads to the sea bed. The array 1 is connected to a towing cable 4 by way of a vibration isolation coupling 5. A rope tail 6, which reduces any tendency for the array to "snake", is normally (but not necessarily) connected to the rear end of the array 1 by way of another vibration isolation coupling 5.

The towing cable 4 is connected to a winch 7 carried by the vessel 3. With reference now to Figure 2, the array 1 comprises a cylindrical body 10 housing a central, longitudinally-extending reinforcement member 11, which, in this example, is formed and constructed as a strain member so as to accept towing loads 16 applied to the array. A plurality of sensors 12 is distributed within the body 10 of the array, in the proximity of the external surface 13 thereof. (As used herein, the term "proximity" is intended to mean near or at the external surface of the array). As the array 1 of this embodiment is a sound-wave sensing array, the sensors 12 comprise hydrophones, although alternatively, or in addition, the array may carry devices whereby, for example, water depth of the array, ambient water temperature and towing loads may be sensed.

The array body 10 is of circular cross-section, viewed normal to its central axis, which axis is coicident with the longitudinal axis 17 of the central member 11, which is also of circular cross-section.

The central, tow-load accepting reinforcement/strain member 11 of this example comprises a copper-clad, multi-strand wire rope, enclosed within a sheath 14 of dielectric material. (Polyethylene). The dielectric sheath 14 is enclosed within a screening structure, comprising a copper braid 15.

The braid 15 is enclosed by a first inner sheath 20, which is itself enclosed by a second inner sheath 21. P.T.F.E. tape 22 is wound around the sheath 21 and the sheaths 20, 21 and tape 22 are enclosed within first and second sheaths 23, 24.

The sheaths 20, 21, 23, 24 are all of plastics material, sheaths 20, 21 being of polyurethane and sheaths 23, 24 of polyethylene.

Buoyancy tubes 25 of NYLON (Registered Trade Mark) are disposed in grooves formed in the bore of the sheath 23. The sheath 14, braid 15 and sheaths 20, 21, 23, 24 are all of circular cross-section, viewed normal to the central axis of the array body 10, and are thus all co-axially disposed.

The sensors 12 are set in modules or beds 30 of polyurethane material, which material serves as an acoustic coupling medium with the ambient sea water. Decoupling material 31 acoustically isolates the beds 30 from surrounding portions of sheaths 21, 23, 24 of array body 10. The outer surfaces 32 of the sensors 12 are near (say 2.0mm) to the external surface 13 of the body 10. Conductor leads 33 connect the sensors 12 and/or associated electronic equipment with the central reinforcement/strain member 11 which also serves as a databus whereby output signals emitted by the sensors are conveyed (via the copper cladding of the member 11, and/or the member 11 itself, the towing cable 4 and slip rings 34) to monitoring and power supply equipment 35 carried by the towing vessel 3. The centrally disposed member 11 is also used to convey electrical power to the array 1.

The central member 11 can be clad with an alternative to copper. For example, a silver coating can be used. Figure 3 illustrates a modification wherein the array is provided with a copper braid 40 co-axially disposed between the centrally-disposed member 11 and the surrounding dielectric sheath 14, thus embracing the member 11 closely. The braid 40, which can be considered part of the central member 11, is also used to convey output signals from the sensors 12 and/or to convey electrical power within the array. The invention provides a compact array of substantially reduced lateral cross-section (say 30.0mm diameter), compared with presently known arrays, thus, for example, reducing drag forces, weight, volume and cost. The invention is not, however, confined to arrays intended to be towed through water by marine craft, or even towed at all. Arrays according to the invention may be carried by various forms of transport. They may also be used in static modes, for example in moored, upright attitudes, or horizontally disposed, resting on, and secured to, the sea bed.

Claims

C L A I M S

1. An array of filamentary form, characterised in that it comprises a body (10) housing a central, longitudinally-extending reinforcement member (11) and a plurality of sensors (12) distributed within the body of the array, in the proximity of the outer surface (13) thereof, wherein said centrally-disposed reinforcement member (11) serves to conveyi signals emitted by the sensors (12).

2. An array as claimed in Claim 1, characterised in that the centrally-disposed reinforcement member (11) also serves to conduct electrical power to the sensors (12).

3. An array as claimed in Claim 1 or 2, towable through water, characterised in that the centrally-disposed reinforcement member (11) is formed and constructed so as to accept towing loads applied

to the array (1).

4. An array as claimed in Claim 3, characterised in that the sensors (12) are used to detect water-borne sound waves.

5. An array as claimed in any one of Claims 1 to 4, characterised in that the centrally-disposed reinforcement member (11) is enclosed by a sheath (14) of dielectric material enclosed in turn by a screening structure (15).

6. An array as claimed in Claim 5, characterised in that the centrally-disposed reinforcement member (11) and screening structure (15) are in turn enclosed by inner (20) and outer (21) co-axial sheaths of plastics material.

7. An array as claimed in any one of Claims 1 to 5, characterised in that the sensors (12) are set in beds (30) of acoustic coupling material, the beds (30) being acoustically isolated from surrounding portions of the body (10) of the array.

B. An array as claimed in any one of Claims 1 to 7, characterised in that a structure (40) embraces the centrally-disposed reinforcement member (11) and the sheath (14) of dielectric material, and serves to convey output signals from the sensors (12) and/or to convey electrical power within the array (1).