WO2015000021A1

WO2015000021A1 - A support structure

Info

Publication number: WO2015000021A1
Application number: PCT/AU2014/000692
Authority: WO
Inventors: Brett Gardiner RANKIN; Andrew James Carpenter
Original assignee: Outer-Rim Developments Pty Ltd
Priority date: 2013-07-05
Filing date: 2014-07-04
Publication date: 2015-01-08
Also published as: AU2014286914B2; AU2014286914A1; CA2916738A1

Abstract

The invention discloses a support structure for an airborne electromagnetic or induced polarization array. The support structure has a frame in the form of a loop wherein the frame contains a plurality of inflatable elongate members that are adapted to be attached together in an end-on-end manner to form the loop, A number of suspension cables are joined to the frame at spaced and are adapted to be attached to a tow rope of an aircraft for suspending the frame therefrom so that the frame can support a transmitter and/or a receiver of the electromagnetic or induced polarization array.

Description

TITLE

A SUPPORT STRUCTURE FIELD OF INVENTION [000.1 ] The present invention relates to a support stru cture,

[0002] More particularly, the present invention relates to a support structure for an airborne electromagnetic or induced polarization array,

BACKGROUND TO INVENTION

[0003] When performing aerial electromagnetic (EM) and induced polarization (IP) surveying of an area it is common practice to deploy a towable transmission and receiver array behind or below an aircraft to generate sensor data relating to the resistivity of an area of land.

|0004] Electromagnetic surveying normally entails the emission of electromagnetic field pulses to generate eddy currents in the ground that induce a secondary current in any underground conductors. The resultant electromagnetic Field can be measured as it decays after the emission of the pulses to map the terrain conductivity. Induced polarization surveying is conducted by inducing a current in the ground area to be surveyed and measuring the decaying potential difference thereof over time. 0005] In both cases it is common practice to use transmission support structure with the coils and loops required to transmit the electromagnetic pulses and induced polarization currents mounted thereto. Such support structures comprise a plurality of elongate members which are joined using elbow connectors to form a polygon or circular shape frame_* A variety of materials have been employed to make these support structure rangi ng from tubes made of metal, fibre glass or even carbon fibres,

[0006] The support structures are commonly heavy and require significant labour to assemble. Furthermore, due to their large sizes, transportation of assembled structures is often not possible and the frame needs to be disassembled before it can be transported to other areas,

[0007] There are also a number of limitations on the size of a support structure that can be built and stil! properly suspended from the aircraft. Any substantial increase in size or weight will have an effect on the performance of the aircraft supporting the support structure during the survey.

[0008] The present invention attempts to overcome at least in part the aforementioned disadvantages of previous support structure in that there is provides a Sight weight frame that may be relatively easily disassembled and transported.

SUMMARY OF INVENTION

[0009] Accordance to an embodiment of the present invention there is provided a support structure for an airborne electromagnetic or induced polarization array, the support structure comprising:

a plurality of inflatable elongate members; and

attachment means for attachin the elongate members together in an end-on-end manner to form a .frame,

wherein the frame is capable of supporting a transmitter and/or a receiver of the electromagnetic or induced polarization array.

[0010] The frame may be a planar loop being polygonal or circular in shape.

[0011] Each elongate member may comprise at least two tubular sections located adjacent to each other and joined together.

[0012] The tubular sections may be cylindrical.

[0013] The tubular sections may be joined together by straps passing around the tubular sections.

[0014] Each elongate member may be substantially triangular in cross section. [0015] Each elongate member may have a valve port permitting inflation and/or deflation of that elongate member.

[00163 Each elongate member may include a strengthening rod at one end thereof for engaging with an opposed end of a neighbouring elongate member.

[0017] The support structure may include tensioning cables extending between selected elongate members across the frame and co-planar therewith, the tensioning cables being adapted to structurally support the frame to restrict deformation of the frame.

[0018] The support structure may include a plurality of suspension cables joined to the frame at spaced apart intervals.

[001 ] The suspension cables may congregate at a verte located away from the plane of the frame to form a pyramidal shape.

[0020] The suspension cables may be adapted to be attached to a tow line for suspending the frame from an aircraft.

[0021] The respective suspension cables may have differing lengths whereby the. suspension cables attached to an operative leading edge of the frame are shorter than those attached to an operative trailing edge of the frame, in use, assisting the frame in maintaining a substantially horizontal orientation when suspended from an aircraft moving at a survey flight speed,

[0022] The invention extends to an airborne electromagnetic or induced polarization array comprising the support structure as described herein.

[0023] The airborne electromagnetic and induced polarization array may include a transmitter and/or receiver supported by the frame.

[0024] The transmitter and/or receiver may be supported concentrically and co-pianar within the frame. BRIEF DESCRIPTION OF DRAWINGS

[0025] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 3 is a perspective view of a support structure in accordance with an embodiment of the present invention showing a frame joined to a plurality of suspension cables?

Figure 2 is a side view of the support structure shown in Figure 1;

Figure 3 is a plan vie of the frame of the support structure shown in Figure 1 ;

Figure 4 is an enlarged perspective view of an elongate member forming part of the frame of Figure 3;

Figure 5 is an enlarged end view of the elongate member seen along arrow V in Figure 4;

Figure 6 is an enlarged side view of a first end of the elongate member indicated by arrow VI in Figure 5; and

Figure 7 is an enlarged side view of a second end of the elongate member indicated by arrow VTI in Figure 5,

DESCRIPTION OF EMBODIMENT

[0026] Referring to Figures 1 to 3 of the drawings, there is shown a support structure in accordance with an embodiment of the invention, being generally indicated by reference numeral 10. The support structure 10 is adapted to support an airborne electromagnetic or induced polarization array by suspending it from an aircraft during use,

[0027] The support, structure 10 includes a planar frame 12 formed by plurality of inflatable elongate members 14 that are releasably attached to each other in an end-o -end manner to form a closed loop being polygonal or circular in shape. In the exemplary embodiment shown in the drawings, the frame 12 has a circular shape thereby, in use, to substantially remove null points in an electromagnetic field pulse generated by the array supported by the support structure 10,

[002 S] One of the elongate members 14 is more clearly shown in Figures 4 to 7, The elongate member 14 is formed by at least two similar cylindrical or tubular sections 16, being generally sausage- like in appearance, which are located adjacent to each other and joined together by a number of straps 18 passing around the tubuiar sections 16 at various locations long their length, in the exemplary embodiment, the elongate member 14 is constituted by three tubular sections 16 being arranged in a substantially triangular shape when seen in cross section. However, it is aiso envisaged that the elongate member 14 can be formed by only a single tubular section 16. in the latter case, the elongate member 14 can optionally be provided with internal dividing walls to provide separate internal compartments.

[0029] The elongate member 14 and/or each tubular section 16 is made of a gas impervious flexible material. In one embodiment the material contains braided fibers defining the surface of the tubuiar sections 16, with the fibers following continuous left and right spiral paths over the length thereof. The material also has axial fibers contained within spaces formed between the braided fibers. The tubular sections 16 can be made gas impervious by either coating or impregnating the braided fibers with an eiastomeric material o by providing a synthetic eiastomeric lining bladder within the cylinder defined by the braided fibers. In an alternative embodiment, the material can be cloth or canvas sheet material also being impregnated with the eiastomeric material or enclosing the eiastomeric lining bladder.

[0030] The elongate member 14 and/or each tubular section 16 has a valve port 20 permitting the inflation or deflation thereof. The inflation will normally be performed by pumping air into the tubular section 16, but optionally other gases could be used, such as helium. In its deflated state the elongate member 14 is flexible and can be rolled up or manipulated into any desired shape, whereas in its inflated state the elongate member 14 has a certain structural rigidity.

[0031] At the opposed ends of the elongate member 14 there are provided corresponding quick release clips 22 for joining neighbouring elongate members 14 to each other erid-on-end to form the loop shaped frame 12. Any number of elongate members 14 can be joined together depending on the size of the frame 12 that is required. The elongate member 1 further includes at least one, but preferably multiple, strengthening rod 24 extending longitudinally beyond one end thereof for engaging with an opposed end of a neighbouring elongate member 14 in the frame 12, Thereby the rod 24 traverses the end-on-end join between neighbouring elongate members 14 and restiicts excessive bending of the frame 12 at the join and transverse forces being applied to the clips 22, The rods 24 are either secured to the elongate members 14 by the straps 18 or by insertion into pocket sleeves,

{0032] Each rod 24 can be in the form of a rigid hollow tube, chosen for its strength and weight characteristics. Alternatively the rod 24 can be an inflatable tube having a high internal pressure.

[0033] Referring to Figure 3, after the frame 12 loop is formed, a number of tensioning cables 26 are joined thereto so as to extend between various selected elongate members 14 across the frame 12 and co-planar therewith. The tensioning cables 26 provide a tension force within the frame 12 to stracturaily support the frame 12 and restrict deformation thereof so that it retains a desired shape. As such, the tensioning cables 26 are arranged to engage with adjacent or nearly adjacent elongate members 14 (as shown in Figure 3), resulting in a Sattjcework of tensioning cables 26 near to the frame 12 so as to leave an open central area within the frame 12, Alternatively the tensioning cables 26 can also be arranged as spokes extending radially or directly across the frame 12. The rods 24 assist the tensioning cables 26 in maintaining the desired shape of the frame 12,

[0034] As shown in Figures 1 and 2_S the support structure 10 is formed by attaching a plurality of suspension cables 28 to the frame 12 at discrete spaced apart intervals, The suspension cables 28 congregate at a vertex 30 located away from the plane of the frame 1.2 so that the. support structure has a pyramidal shape. The vertex 30 is adapted to be joined to a tow line 36 so as to enable the support structure 10 to be suspended beneath an aircraft.

[0035] Preferably, the suspension cables 28 have differing lengths and are arranged such thai those being attached to an operative leading edge 32 of the frame 12 are shorter than those being attached to an operative trailing edge 34 of the frame 12, The differing lengths cause the vertex 30 to be offset from the centre of the frame 12, and thereby assist the frame 12 in maintaining a substantially horizontal orientation when suspended below and towed by the aircraft at a survey flight speed,

[0036] The support structure 10 may further comprise a receiver shell which is disposed substantially concentrically and co-planar within the frame 12. [0037] In use, the elongate members 14 are laid out in the required positions, to create the requisite shape of frame 12, and the neighbouring elongate members 14 are joined to each other by the clips 22 and the rods 24, Thereafter the elongate members 14 are inflated by bringing the valve ports 20 in communication with a source of pressurised gas or air,

[0038] After inflation, the tensioning cables 26 are fixed between the desired elongate members 1 and the amount of tension force applied to stabilise the shape of the frame 12. The suspension cables 28 are then also attached to the frame 12 and joined to the aircraft's tow line 36 at which time the electromagnetic or induced polarization array can be arranged on the support structure 10.

[0039] In addition to providing structural rigidity to the frame 12, the latticework of tensioning cables 26 act together with the frame 12 to provide the support to which the electromagnetic or induced polarization array and/or the receiver shell can be secured.

[0040] After use is finished, the support structure 10 can be collapsed and disassembled by deflating the elongate members. This is done either fay simply opening the valve ports 20 to allow the air to vent to the atmosphere from the elongate members 14 or by applying a suction force to the valve ports 20 to more quickly exhaust the air from the elongate members 14.

[0041] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Claims

1. A support structure for an airborne electromagnetic or induced polarization array, the support structure comprising;

a plurality of inflatable elongate members; and

attachment means for attaching tie elongate members together in an end-ou-end manner to form a frame,

2, A support structure as claimed in claims 1 , in which the frame is a planar loop being polygonal or circular in shape.

3, A support structure as claimed in claim 1 or 2, in which each elongate member comprises at least two tubular sections located adjacent to each other and joined together.

4. A support structure as claimed in claim 3, in which the tubular sections are cylindrical

5. A support structure as claimed in claim 3 or 4, in which the tubular sections are joined together by straps passing around the tubular sections.

6, A support structure as claimed in any one of the preceding claims, in which each elongate member is substantiall triangular in cross section.

7, A support structure as claimed in any one of the preceding claims, in which each elongate member has a val ve port permitting inflation and/o deflation of that elongate member.

8, A support structure as claimed in any one of the preceding claims, in which each elongate member includes a strengthening rod at one end thereof for engaging with an opposed end of a neighbouring elongate member.

9. A support structure as claimed in any one of the preceding claims, which includes tensioning cables extending between selected elongate members across the frame and co-planar therewith, the tensioning cables being adapted to structuraUy support the frame to restrict deformation of the frame.

10. A support structure as claimed in any one of the preceding claims, which includes a plurality of suspension cables joined to the frame at spaced apart intervals.

1 1. A support structure as claimed in claim 10, in which the suspension cables congregate at a vertex located away from the plane of the frame to form a pyramidal shape.

12. A support structure as claimed in claim 10 or 1 1, in which the suspension cables are adapted to be attached to a tow line for suspending the frame from an aircraft.

13. A support structure as claimed in any one of claims 10 to 12, in which the respective suspension cables have differing lengths whereby the suspension cables attached to an operative leading edge of the frame are shorter than those attached to an operative trailing edge of the frame, In use, assisting the frame in maintaining a substantially horizontal orientation when suspended from an aircraft moving at a survey flight speed.

14. An airborne electromagnetic or induced polarization array comprising the support structure as claimed In any one of the preceding claims,

15. An airborne electromagnetic and induced polarization array as claimed in claim 14, which includes a transmitter and/or receiver supported by the frame.

16. An airborne electromagnetic and induced polarization array as claimed in claim 15, in which the transmitter and/or receiver is supported concentrically and co-planar within the frame.