GB2397439A - Flexible collapsible radar corner reflector - Google Patents

Abstract

A collapsible radar reflecting device 7 consisting of flexible panels that, when in use, form mutually orthogonal intersecting planes. The collapsed reflector is deployed and erected by tension exerted upon the attached lines 6. When in a fully collapsed state the reflector is designed to be essentially planar and may be folded up to a small volume for storage. Planarity is attained through splitting one of the panels forming one of the intersecting planes into two parallel surfaces over 50% of its surface (13, 14). The structure is then able to collapse by these adjacent non-bonded panels hinging apart about an axis of common intersection.

Description

FLEXIBLE COLLAPSIBLE CORNER RADAR REFLECTOR

The described invention relates to the field of emergency, or temporary, radar reflectors for use as an aid in the location of lost or injured personnel in marine or land-based environments where precise location is difficult due to adverse weather conditions, difficult terrain, imprecise knowledge of position or poor light. An embodiment of the invention may be used as a location marker, for example, for equipment or persons buried by snow resulting from an avalanche. An alternative use is as a decoy device for radar guided missiles.

Such radar reflecting devices are well known. These devices all suffer from the disadvantage that, when collapsed or deflated they are too large to fit into a small pocket on a garment, and thus necessitate a separate container to be carried. Those devices described as fully collapsible often do not deploy automatically. Furthermore existing designs are invariably difficult to fabricate, often needing multiple fixture points tor the reflector to the interior of a balloon structure.

An aim of this invention is to provide a collapsible radar reflector, for example, for marine or wilderness use, which is radar reflective, easy to deploy, collapsible, flexible when collapsed, and may be kept when in the folded, collapsed state within a small volume.

In one aspect the invention provides a collapsible corner radar reflector comprising a plurality of sheets of flexible radar-reflective material, said sheets of flexible material being attached to one another such that, during deployment, the material is pulled into a deployed configuration providing a plurality of radar reflective corners, two of said sheets being joined along a line and each being provided with a cord attachment spaced away from said line, at least one cord being attached to said cord attachments such that when said cord is pulled in a deploying direction said two sheets are pulled to face one another to cause said radar reflector to adopt said deployed configuration.

In another aspect the invention provides a plurality corner radar reflector comprising intersecting surfaces that collapses to occupy a small volume by means ol one of the intersecting surfaces being divided in its plane over about half of its area, which can then hinge apart about an axis of common intersection allowing the flexible radar reflector to collapse to give an essentially planar structure, which may then be reduced in size, by further folding.

Accordingly, an embodiment of this invention provides a corner type radar retroreflector that is collapsible and foldable to a small volume but when deployed opens to form a corner radar reflector. The device may be deployed by means of a lighter than air, for example helium gas filled, balloon, by means of a aerofoil/kite, by means of a lighter than air balloon or aerofoil/kite used in conjunction, or when used as a decoy for radar guided missiles by means of a parachute and ballast weight. The corner radar reflector may also be encased in a radar permeable envelope and its structure maintained by the pressure of a lighter than air gas.

Preferably the corner radar retroreflector is made of a flexible radar reflective material such as foil or metal-coated PET (or other thin polymeric) film.

Preferred embodiment(s) of the invention will now be described with reference to the accompanying drawings in which: FIGURE 1 shows a schematic view of a collapsible radar reflector when deployed and in use as a personal location device in the marine environment. Two preferred embodiments arc detailed, (A) shows the reflector suspended below the balloon, whilst (B) illustrates how the reflector may be incorporated within the balloon.

FIGURE 2 shows a perspective view of the corner radar retroreflector 7, showing its axis of common intersection 12.

FIGURE 3 shows, by a perspective view, a suggested construction of the corner radar reflector.

FIGURE 4 shows both a plan and perspective view ol the fully erect corner radar reflector.

FIGURES 5-9 are plan and perspective views of the corner radar reflector partially erected, illustrating the mechanism by which the invention collapses.

FIGURE 10 shows how the fully collapsed structure may be folded to occupy a small volume FIC,[]RE 11 is a perspective view that shows a mechanism by which the collapsible radar reflector deploys.

FIGURE 12 is a perspective view that shows an alternative mechanism by which the collapsible radar reflector deploys.

As shown in I;igure 1, the collapsible corner radar reflector 7 may be utilised within a personal locator device 11 for use in a marine environment 2 in conjunction with other rescue aid devices, such as the flashing LED 8, not illustrated. It is envisaged that the radar reflector 7 may be deployed suspended beneath a balloon 9 filled with a lighter than air gas as shown in Figure la. The tension imparted by the balloon 9 upon its flexible gas line 6 will open and erect the corner radar reflector 7 as detailed in Figure 11 and 12. A further embodiment of the invention is also illustrated in Figure lb whereby the radar reflector is retained within a radar permeable balloon 10 containing a lighter than air gas. When not in use the personal locator 11, incorporating the radar reflector 7, in the fully collapsed and folded state 7d as detailed in Figure 10, is retained inside a small pocket 5, for example, on the shoulder of a lifejacket 4. The pocket 5 is held fast by an easily released material, for example Velcro A, and also contains a separate balloon 9 if required as in Figure la. Also fixed to the lifejacket is a small cylinder of a lighter than air gas, for example helium, connected to a valve that opens automatically upon prolonged immersion in water (not shown). The valve may be connected by a flexible gas line 6, either to a radar permeable envelope 10 containing the reflector 7 as shown in Figure l b, or initially to the radar reflector 7 and then a balloon 9 as illustrated in Figures la and l l, or just to a balloon 9 with the radar reflector 7 separately tethered 20, 19 to both balloon and lifejacket as shown in Figure 12. The line 6, or 19/20, should be of sufficient length that both the balloon 9 and the reflector 7, or combined balloon/reflector l 0 are, when in use, kept at sufficient height above sea level 3 to be easily visible to radar. If, for the latter example, the wearer 1 of the life jacket 4 fell overboard into the sea 2, then the balloon would automatically inflate. The inflating balloon 9, or 10, would open the pocket 5 on the life jacket 4 and escape pulling the collapsed corner reflector 7d with it. When fully inflated the balloon, which would ideally be of a highly visible colour, exerts enough tension upon the reflector 7 to pull it into shape, via 7c, and 7b in Figure 10, and subsequently Figures 9 to 5 and also, maintain its fully opened shape as shown in Figures 2, 4 and 1.

As shown in Figure 2 when erected the device forms a corner type radar reflector 7 consisting of a series of vertical (in the diagram) intersecting surfaces, which have an axis of common intersection 12, linked by an equatorial intersecting surface.

Figure 3 illustrates the suggested preferred basic components of the reflector design prior to assembly. The reflector is composed of intersecting surfaces formed by sheets of flexible radar reflective material. Though square sheets are illustrated other shapes could be utilised. Parts 13 and 14 are joined such that they form one of the intersecting surfaces, which is divided over half of its surface area, as indicated by the shaded area. Part 15 may then be joined to the composite of parts 13 and 14 by means of the slots E and F and fixing along the seam to form a second intersecting surface.

Part 16 is cut in two along a diagonal, giving parts 16a and 16b,which form the remaining intersecting surface when in the deployed position. These are fixed to both part 15 by means of the slot C aligning with D, in the case of 16a, and slot B aligning with slot A for 16b. Part 16ais then joined along its longest edge to the face of part 14 by taping, gluing, etc. The same is done to join part 16b to part 13. The result will be the collapsible radar reflector as illustrated in Figures 4 to 9.

Figures 4 to 9 show sequentially the stages of collapse for the radar reflector. At partial erection the device has limited structural integrity as a corner reflector, the mechanism by which the horizontal equatorial component 16a and 16b may be folded for compactness is clearly visible. The areas of 13 and 14 not bonded in Figure 3, which are abutting in the erected radar reflector, are able to move apart by pivoting about the axis of intersection 12 in Figure 2. Figure 4 shows the fully erect structure where the adjacent surfaces 13 and 14 are held together, by the tension imparted by a mechanism such as shown in Figure 11 and 12, or by the pressure of a lighter than air gas when the device is enclosed within a radar permeable envelope. Figures 5 and 6 illustrate the radar reflector in the initial stages of collapse with the shaded areas of 13 and 14 moving apart. The flexible panel forming one of the vertical intersecting surfaces 15 starts to hinge close about axis 12 and the horizontal equatorial components 16 start to collapse by folding in the manner shown. Figure 7 shows the radar reflector in the half erected state. Figures 8 and 9 show the initial stages of erection from the reverse perspective view to Figures 4 to 7, illustrating the mechanism by which the components 16a and 16b fold when collapsed. Figure 9 shows the structure at near full collapse. When not in use the reflector is folded as in Figure l O and maybe retained in a small pocket with the balloon, gas cylinder and inflation device, or other method of deployment (not shown). Where the reflector is contained within a radar permeable envelope, as illustrated in Figure lb, the faces of the octahedron are covered with a radar permeable material (not shown). The envelope is preferably continuous and is ideally fixed only at the edges of the non- bonded area of 13 and 14, facilitating easier construction whilst allowing a collapsible structure. To enable quick inflation the vertices of the octahedra may be cut away slightly, or holes placed in the component panels of the reflector to allow the passage of gas within the structure (not shown).

Figure 10 illustrates that, in this case, when the reflector 7 is fully collapsed, the mechanism for which is shown in Figures 4-9, it forms, in this instance, a planar triangle 7b enclosed within the internal faces of 13 and 14. This may be further reduced in size by folding along the lines denoted H and G in Figure l 0. This results in the planar square structure 7c illustrated, which itself may be folded about the line J to form a compact rectangular package 7d that may be easily stored in, for example, a small pocket on a life jacket (not shown).

Figure l l illustrates a mechanism by which the radar reflector 7 may be deployed.

The collapsible radar reflector is deployed by means of tension being exerted upon a line 6 in opposing directions, away from the collapsible radar reflector. The line 6 is also fixed to the reflector 7 at the points marked 17, before passing through the apertures 18 in components 13 and 14. As tension is exerted upon the line 6, the line is drawn through apertures 18 pulling the shaded faces 13 and 14 of the divided intersecting surface towards each other so that they pivot about the axis of intersection, 12 in Figure 2, through the partially collapsed structure illustrated in Figures 9 to 5, until adjacent as in the fully erect structure in Figure 2. If the collapsible radar reflector is deployed by means of being suspended beneath a balloon containing lighter than air gas 9, as shown in Figure la, then the line 6 may represent a narrow, flexible gas hose that is tethered to the garment by means of the gas cylinder and valve (not shown). It is also fastened securely to the balloon 9 which when inflated with a lighter than air gas, for example helium, exerts a tension upon 6.

This tension pulls the flexible corner reflector into shape, from the collapsed folded structure as shown in Figure lO, through the partially collapsed structures illustrated in Figures 9 to 5 to the fully erect structure as given in Figure 2. In strong wind conditions the balloon may be augmented by a aerofoil/kite (not shown). The flexible gas line 6 is fixed such that the rejector 7 is suspended at a reasonable height above the person 1, as shown in Figure la. Ii' the collapsible radar reflector is deployed by means of being suspended beneath an acroi'oil/kite then 6 may represent a tethered line, with tension exerted upon it by the action of the aerofoil/kite. Additionally, if the collapsible radar reflector is deployed by means of being suspended beneath a parachute then 6 may represent a line, with tension exerted upon it by means of a ballast weight below the device acting against the drag of the parachute above the device.

Figure 12 illustrates a further mechanism by which the radar reflector 7 may be deployed. The collapsible radar reflector is deployed by means of tension being exerted upon line 19 and line 20 in opposing directions, away from the collapsible radar reflector. As tension is exerted upon the loop in line 20, the loop is drawn through apertures 18 pulling the shaded faces 13 and 14 of the divided intersecting surface towards each other so that they pivot about the axis of intersection, 12 in Figure 2, through the partially collapsed structure illustrated in Figures 9 to 5, until abutting in the fully erect structure as given in Figure 2. Tension may be exerted on line 20 by a balloon containing lighter than air gas, as illustrated in Figure la, or suspended beneath an aerofoil/kite, or a combination of the two devices when line 19 is anchored, for example to the person 1 in Figure la. In another example, not shown, where the collapsible radar reflector might be incorporated into a decoy device for radar guided missiles, tension may be exerted upon line 20 by some weight acting against the opposing drag of a parachute connected to line 19.

Claims (14)

1. A collapsible corner radar reflector comprising a plurality of sheets of flexible radar-reflective material, said sheets of flexible material being attached to one another such that, during deployment, the material is pulled into a deployed configuration providing a plurality of radar reflective corners, two of said sheets being joined along a line and each being provided with a cord attachment spaced away from said line, at least one cord being attached to said cord attachments such that when said cord is pulled in a deploying direction said two sheets are pulled to face one another to cause said radar reflector to adopt said deployed configuration.

2. A collapsible corner radar reflector as claimed in claim I wherein said two sheets comprise portions of a single sheet.

3. A collapsible corner radar reflector as claimed in claim I or 2 wherein said sheets of flexible radar reflective material comprise sheets of metallised or conductive plastic film.

4. A collapsible corner radar reflector claim 1, 2 or 3 wherein in a collapsed state the radar renector is substantially planar and foldable.

5. A collapsible corner radar reflector as claimed in any preceding claim further comprising deployment means, said deployment means comprising a parachute to support said collapsible radar reflector and a weight to pull said at least one cord in said deploying direction.

6. A collapsible corner radar reflector as claimed in any preceding claim wherein said at least one cord comprises a cord loop.

7. A personal location aid comprising the collapsible corner cable reflector of any preceding claim.

8. A plurality corner radar reflector comprising intersecting surfaces that collapses to occupy a small volume by means of one of the intersecting surfaces being divided in its plane over about half of its area, which can then hinge apart about an axis of common intersection allowing the flexible radar reflector to collapse to give an essentially planar structure, which may then be reduced in size, by further folding.

9. A collapsible plurality corner radar reflector as claimed in claim 8 where the collapsible corner reflector is contained within, or suspended beneath, a balloon that may be deflated and collapsed to occupy a small volume and may be filled with lighter than air gas.

10. A collapsible plurality corner radar reflector as claimed in claim 8, or claim 9, which is deployed by means of being suspended beneath a aerofoil or kite, which may also be collapsible.

11. A collapsible plurality corner radar reflector as claimed in claim 8 where the collapsible corner reflector is deployed by means of being suspended beneath a parachute by a weight.

12. A collapsible plurality corner radar reflector as claimed in claim 8 where the surfaces of the corner reflector are fabricated from a flexible radar reflective material.

13. A collapsible plurality corner radar reflector used as a personal locator as claimed in any one of claims 8 to 12 incorporating another personal location aid such as a flashing light, or bright colour.

14. A collapsible plurality corner radar reflector substantially as herein described.