REFLECTOR

Abstract: A reflector device (3) may be mounted in a hollow housing (2) adapted to fly in ambient air. The reflector device (3) may be formed from a coating on the surfaces of blocks, the coating being metal or dielectric. Reflecting surfaces whether self supporting or not may be formed as intersecting circles or polygonal (more than four sides). They may be suspended in a housing (2) adapted to fly either directly or indirectly by means of an intermediate body within the housing.

Description: REEIiECTOR Reflectors providing a substantially uniform response in all directions have been made frαn three mutually orthogonal plates of metal. The plates may intersect along a centre line. In order to withstand exposure to weather, the metal has to be of substantial thickness and so the reflector is heavy which is inconvenient, particularly for exarrple when the reflector is desired to be hoisted to the masthead of a sailing dinghy. According to one aspect of the present invention there is provided a reflector corrprising reflecting surfaces arranged in mutually inclined planes, the surfaces being formed on blocks of lightweight support material. The surfaces are preferably mutually orthogonal. The support material blocks are secured together with a metallic or dielectric coating on at least one of the facing surfaces, so that the reflecting coatings are not exposed to the weather. Cαrplete protection can be achieved by encapsulating the block assembly and the capsule can provide means for suspending the reflector from a support. The thickness of the coating has only to be sufficient to act as a reflector and not to be self supporting. In the prior art reflectors where the metallised surfacs were self supporting and were in the form of metal plates, the plates were of diamond shape. Whether the metallised surfaces are self supporting or not, we have discovered that by making the shape of individual metallised surfaces circular or at least closely approximating the circular (e.g. polygonal with the number of sides exceeding 4) shape, improved response is achieved. According to another aspect of the invention there is provided a reflector coπprising a plurality of mutually inclined surfaces each of which extends either side of lines on which it inersects another such surface and has a circular or polygonal (with more than four sides) shape. Although this reflector is light in weight, the blocks of support material are bulky. We have discovered that it is possible to support the metallised surfaces on elements within an inflatable envelcpe, the envelcpe being stored in a deflated condition and then expanded for use by the introduction of air or other gas so as to make the envelcpe approach a spherical shape and the internal metallised elements within the envelope will then provide the reflecting surfaces. Thus according to another aspect of the invention there is provided a reflector cαrprising a plurality of mutually inclined surfaces each of which extends on either side of lines in which it intersects another such surface, the surfaces being of elements mounted within an expandable envelcpe. The elements may be of wire mesh or textiles and may include stretch fabrics so as to provide reduced resistance to the expansion of the envelope. In each case, the elements will be coated with metal, preferably silver. The envelcpe can be inflated with air so as to have a density less than unity so that it will then float. Such reflectors can be thrown overboard from a vessel in order to provide a dumπy reflector on the surface of the sea. Alternatively, a lighter gas can be used to inflate the envelope so that the reflectors will rise into the air, either freely flying or tethered to the vessel to provide reflectors in a desired pattern. The tethered reflectors can be hauled back to the vessel when they have served their purpose. The envelopes can be deflated and stored flat for re-use. Although the elements may be mounted directly to the envelcpe, it is preferable that they are secured indirectly to the envelcpe, being secured directly to an intermediate body which itself is mounted within the envelope. In one example, the intermediate body is intially formed as a tube having open ends. This allows the elements to be inserted into the tube frcm one end and secured to its interior wall by any suitable means, such as clamping or stapling as well as by glueing. The ends of the tube are then closed and the tube is mounted within the main envelcpe. The tube and the envelope are inflated so that the tube changes frcm a sausage-shape (the cylinder with closed ends) to approximate to a sphere as its central portion is e_ anded by the inflation. The tube may be of slightly permeable material so that some of the inflating gas (such as helium) can escape through the walls of the tube to inflate the envelope or a separate port may be provided for inflation gas to enter the space between the tube and the envelcpe. After inflation, the tube and the envelope approach each other in approximately spherical shape and the elements within the tube are drawn out to their intended final arrangement to provide a reflector of uniform all-round response. The inflated tube and envelope are then vulcanised so that they stick together. A suitable material for the envelcpe is a rubbery material and the tube should be of the same or at least compatible material so that vulcanisation can take place. The reflectors can be inflated so that they float in the air. The envlσpes can be tethered so that the reflectors float at a predetermined height, thus providing a dummy target at that height, which is selected to be the height of the target the missile directing system is expecting. A dummy reflector left to float on the surface of the sea of directly mounted on a floating raft might be rejected by the missile directing system, since the system may be controlled only to select targets which ressemble for example frigates whose vulnerable area (the engine roc for example) target height will be many metres above the sea surface. A dummy reflector tethered to fly at the many metre height above a floating raft will not be rejected by such a missile system and so will be successful in causing the missile system to believe that it has found a genuine target. According to another aspect of the present invention there is provided a reflector for incident electromagnetic energy, comprising a hollow housing adapted to fly in ambient air and, interiorly thereof, a reflector device for reflecting incident electromagnetic radiation. The housing may suitably cαrprise an envelcpe inflatable with a suitable gas. The reflector device may cαrprise a substantially spherical device. There may be a plurality of discrete spherical reflector devices housed in the housing, for exarrple three. The or each reflector device may cαrprise an aluminised cloth which is elastic and formed into the shape of a sphere. There may be means to position the or each reflector device interiorly of the housing. The positioning means may cαrprise a plurality of separate connectors which extend over substantially the whole surface of the reflector device and which are connected between that surface and the interior surface of the housing. The connectors may cαrprise elasticated material strip connectors which are adapted to maintain the surface of the reflector device in tension, and which may preferably be in tension themselves. The connectors may each be secured in position by engagement at one end with a tab at the interior surf ce of the housing and at the opposite end by a tab at the exterior surface of the reflector device. A reflector embodying the invention is hereinafter described, by way of example, with reference to the accαrpanying drawing, which shows a schematic side elevational view, partly in phantom, of a reflector in the form of a kite balloon. Examples of the invention will now be described with reference to the accαrpanying drawings in which: Figure 1 shows a reflector coxrprising a reflector device withing an inflatable housing Figure 2 is a perspective view of an exemplary reflector device, Figure 3 is a perspective view of one block of Figure 2 and Figure 4 is a detail corresponding to Figure 3 of an alternative embodiment. In Figure 1, there is shown a reflector 1 for incident electromagnetic energy, in this case in the radar range, cαrprising a hollow housing 2 in the form of an inflatable balloon and, interiorly thereof, a reflector device 3 for reflecting incident radar beams. There are three reflector devices 3 in the balloon 2 in the embodiment shown. Each is substantially spherical and is made frcm an aluminised cloth. The spheres 3 are maintained in tension, and thus spherical, by position means in the form of elasticated strip material connectors 4 such as elasticated cloth (only some of which are shown). The connectors 4 extend over the whole surface area of the reflector device 3 and are connected between tabs 5 at one end on the interior surface of the housing 2 and at the opposite end by tabs 6 on the exterior surface of the spherical device 3. The tabs 5, 6 may cαrprise plastic or cloth flaps with holes through which a hook carried by the ends of the connectors 4 engage. Only one set of tabs 5, 6 are shown for clarity. To manufacture the reflector 1 the material of the housing 2 is laid out as a sheet the tabs 5 are positioned as are the reflector devices 3 with the tabs 6 and the connectors 4 are connected up to maintain the reflector devices 3 in position. The material of the housing, suitably nylon coated polyurethane, is then folded so that opposite edges meet and these edges are then heat welded together, leaving fins 7 intact and an inflation nozzle(s) 9 in place. When the housing is inflated with say air or helium, the reflector 1 can be flσwin in air say from the mast-head of a yacht. The reflectors 3 inside reflect incident radar energy so that the position of the yacht can be identified. The configuration of the balloon 2 produces dynamic lift and the fins 7 and rudder 8 provide dynamic stability. The rudder 8 keeps the balloon heading into wind and therefore provides a required "signature" whereby the identity of the yacht can be ascertained. The reflector 1 may be tethered by suitable tethers 10. The exeπplary reflector device of Figure 2 cαrprises eight identical blocks. One block is shown in Figure 3. The block is a regular cube with one coiner bevelled away, the edges leading so that corner being about one fifth of the length of the full edges of the cube. The three remaining square sides of the cube are coated with aliiminium, by any convenient method. The coating could alternatively be of dielectric material since this also has reflecting properties for certain radiation. The eight blocks are secured together, square face - to - square face, to form a body approximating to a sphere, as can be seen in Figure 2. The metal coatings are only exposed at their edges and this exposure can be protected by encapsulating the structure, for exarrple in shrink wrap film or a more durable plastics coating. A supporting member (not shown) can be affixed to the envelcpe of the encapsulation or secured in between two blocks, so that the reflector can be secured to another structure or attached to a cable. The alternative e bodiirent of Figure 4 shows the individual block as an exact eighth part of a sphere. The quarter circle surfaces are metal coated and secured together so that the full reflector is a sphere divided down three mutually orthogonal planes by the metallic coating. The blocks are of any suitable lightweight material which does not hinder the passage of radiation. Conveniently they are of foamed plastics material. The blocks are conveniently secured together by glueing the metallic surfaces. The metallic coating can be applied to one or (preferably) both of the facing surfaces between adjacent blocks. The various aspects of the invention can be used singly or in any combination.

Claims: CLAIMS: 1. A reflector for incident electrαnagnetic energy, cαrprising a hollow housing adapted to fly in arrbient air and, interiorly thereof, a reflector device for reflectiing incident electromagnetic radiation. 2. A reflector as claimed in Claim 1 wheein the housing cαrprises an envelope inflatable with a suitable gas. 3. A reflector as claimed in Claim 1 or Claim 2 wherein the reflector device cαrprises a substantially spherical device. 4. A reflector as claimed in Claim 3 wherein the or each reflector device cαrprises an aluminised cloth which is elastic and formed into the shape of a sphere. 5. A reflector as claimed in any one of Claims 1 to 4 cαrprising means to position the or each reflector device interiorly of the housing. 6. A reflector as claimed in Claim 5 wherein the positioning means comprises a plurality of separate connectors which extend over substantially the whole surface of the reflector device and which are connected between that surface and the interior surface of the housing. 7. A reflector as claimed in Claim 6 wherein the connectors cαrprise elasticated material strip connectors which are adapted to maintain the surface of the reflector device in tension. 8. A reflector cαrprising reflecting surfaces arranged in jutually inclined planes, the surfaces being formed on blocks of lightweight support material. 9. A reflector cαrprising a plurality of mutually inclined surfaces each of which extends either side of lines on which it intersects another such surface and has a circular or polygonal (with more than four sides) shape. 10. A reflector cαrprising a plurality of mutually inclined surfaces each of which extends on either side of lines in which it intersects another such surface, the surfaces being of elements mounted within an expandable envelope.

Inventors: TUSCH KLAUS NORBERT, TUSCH, KLAUS, NORBERT
Applicants: COLEBRAND LTD, COLEBRAND LIMITED
Application year: 1991
Main classification: H01Q15
IPC codes: H01Q15