GB2456808A

GB2456808A - Collapsible corner reflector with a rapid deployment system

Info

Publication number: GB2456808A
Application number: GB0801316A
Authority: GB
Inventors: Andrew Barlow; John Mobsby
Original assignee: Chemring Countermeasures Ltd
Current assignee: Chemring Countermeasures Ltd
Priority date: 2008-01-24
Filing date: 2008-01-24
Publication date: 2009-07-29
Anticipated expiration: 2028-01-24
Also published as: GB2456808B; GB0801316D0

Abstract

A collapsible corner reflector assembly comprises multiple collapsible corners each with three reflecting planes at right angles to one another, when in a deployed condition. The reflectors are supported by six stressed resilient struts. A first group of three struts 2b are attached to a piston and may be stored in a parallel state within a piton tube 6. A second group of three struts 2a are attached to a hub 3 arranged at a first end of the piston tube 6 with a hole through which the first three struts 2b may be deployed. A propellant is disposed at the second end of the piston tube 6. Activation of the propellant drives the piston such that the first group of struts 2b slide through the hole in the hub 3 in the axial direction of the piston tube 6 causing the corner reflector to be deployed. The stress in the struts and the reflective fabric material may be arranged to hold the reflector in its deployed condition. The second group of struts 2a may be stored in a parallel manner around the outside of the piston tube 6. The propellant means may be screwed on to the second end of the piston tube 6 and may involve a small volume of pyrotechnic gas. The hub 3 may be clipped to the first end of the piston tube 6 such that it disengages from the tube 6 when the reflector is fully deployed. The length of the struts may be adjustable to accommodate a range of reflector sizes.

Description

CORNER REFLECTOR

This invention relates to corner reflectors for use as a countermeasure against radar ranging and detecting apparatus and in particular to a compact arrangement for storing and deploying such a reflector.

Corner reflectors are well known, they employ three reflecting planes mutually at right angles. The reflectors are typically stored in a collapsed condition erecting to form the three mutually perpendicularly planes on deployment from a payload. Various storage/erection configurations are known, these include variations as diverse as inflatable frames provided externally of the reflector planes and collapsible metal frames which define the perpendicular axes of the three reflecting planes. I... * 4 4...

The present invention seeks to provide a novel erection arrangement *I*I : which provides for a reflector of minimal volume and weight when packed combined with a strong support structure when erect. S. * *

* In accordance with the present invention there is provided collapsible S..

corner reflector assembly containing multiple collapsible corners, each collapsible corner comprising three reflecting planes disposable mutually at right angles and supported by six stressed struts disposed in two sets of three struts, the two sets of struts being arranged to occupy opposing corners of the fully disposed reflector assembly, the first set of struts being pinned at a common terminus to a piston, the piston being disposed in the bore of a piston tube with the struts aligned substantially in parallel with the axis of the piston tube, a hub having a central aperture through which the first set of struts are arranged to slide in an axial direction on deployment of the piston by means of a propellant device and an external perimeter surface to which the second set of flexible struts is hingedly attached, the hub being situated at a first end of said piston tube and the propellant device disposed at a second end of the piston tube.

In use, when the piston is deployed, the first set of struts is expelled through the central aperture of the hub. Since all struts are commonly connected by radar reflective fabric panels which, in the fully deployed corner reflector form the mutually perpendicular planes, the second set of struts is simultaneously pulled into its fully deployed position. Thus, when fully deployed, the framework of the corner reflector is comprised of the six struts and the hub which sits centrally of the structure.

The collapsible corner reflector assembly typically contains 8 collapsible corners.

** The propellant device conveniently comprises a small volume pyrotechnic *:::* gas generator configured on initiation to provide a gaseous release which drives the piston up the piston tube. Optionally, the gas generator is * . S. attached to the piston tube by means of a screw thread. S..

Desirably, the piston tube is provided with a radially extending recess into * which the hub is releasably clipped. This recess provides an anchor point * for the hub during inflation of the corner reflector. Conveniently, deployment of the piston is configured so as to effect release of the hub from the recess once the reflector has been fully deployed; this allows parasitic weight of the now spent propellant device to be released keeping the free fall weight of the corner reflector to a minimum.

Optionally, the struts are configured to be adjustable in length to accommodate a range of reflector sizes.

The radar reflective fabric may be of any known material and is optionally sewn or welded to form each orthogonal corner.

By way of example, an embodiment of the invention will now be further described with reference to the accompanying Figures in which; Figure 1 shows generally the configuration of a fully deployed corner reflector in accordance with the invention Figure 2 shows a cut away view illustrating the propellant device, piston arrangement and countermeasure positioned in the piston tube.

Figure 3 shows the arrangement of the struts with respect to the hub prior to deployment of the corner reflector. * .* * S * * **

Figure 4 shows chronological stages in an inflation sequence of a corner *..* reflector in accordance with the invention. ass. *

As can be seen from Figure 1, an inflated' free falling corner reflector 1 :. consists of an ultra-lightweight sewn/welded assembly of radar reflective * fabric 4, tensioned orthogonally by the six curved stressed struts 2a, 2b *55 * which are co-located about the central hub 3 which is positioned at a central hole in the fabric assembly. Struts opposing each other balance the forces within the fabric and a state of equilibrium is achieved.

More specifically, the struts are provided in two sets of three struts, a first set is marked 2a and the second 2b. The set 2a are each hingedly attached to hub 3, the second set 2b is hingedly connected to the piston 5.

Figure 2 illustrates the corner reflector when packed into the piston tube prior to deployment. A piston 5 sits in piston tube 6. Struts 2b are hinged to the piston. A gas generator body 12 is screwed into the annular recess 6a of the piston tube 6. The gas generator body 12 includes a takeover pyrotechnic 7, a delay 8, an igniter 9,10 and a gas generator pyrotechnic grain ii. In use, when the igniter 9 is ignited, piston 5 is driven up tube 6 forcing the struts 2b through a central aperture in a hub (not shown) around which the struts 2a are hinged. This causes inflation of the corner reflector.

It will be appreciated that, for clarity only, the radar reflective fabric panels are omitted from the figure but would be present in practice.

Figure 3 shows the arrangement of the struts 2a, 2b about the hub 3 which sits a top piston tube 6. Also shown is a plurality of anchor points 13 to which the radar reflective fabric panels 4 may be fastened. * .* * S * * S.

Figure 4 shows 4 chronological steps during the inflation of the corner *5SS reflector. Step Si shows the assembly packaged in the piston tube. Step S...

*..: Sz shows the movement of the struts immediately following ignition of the gas generator as the piston moves. As can be seen, as the first set of struts passes through the centre of the hub, the second set of struts is pulled outwards. The free-fall assembly is erected by the gas pressure *55 * produced by a small volume pyrotechnic gas generator 7,8,9,11. Three of the struts (inner struts) are pinned to a piston which runs in the bore of the piston tube 5. At one end of the tube the central main hub clips to an internal recess whilst at the other end the gas generator is attached by a screw thread. On initiation of the gas generator, the gas pressure acts on the piston driving the inner struts out through the central hub. The reflector begins to inflate'. The strut assembly is configured such that the three inner struts and the three outer struts, which are pinned to the central hub, are arranged so that they occupy opposing corners of the sewn fabric assembly. As the inner struts are driven out through the central hub, the outer struts are pulled, by their common attachment to the fabric, towards their final position.

A point is reached S3 before the inner struts are fully expelled where the strut/fabric assembly chokes'. The fabric becomes taught and the struts begin to take on the inflated loading. In order for the mechanism to become fully deployed the struts are driven further and are required to bend. The struts reach their collapsing compressive load and bend as the sewn fabric assembly restricts further extension. The strut assembly over-centre locks into position as the piston reaches the central hub at the top of the gas pressure tube. The inflated structure is maintained by the energy stored in the compressed bent struts.

In step S4, the inflated free-fall structure is released from the gas pressure tube by the action of a feature on the piston unclipping the central hub from the recess in the top of the tube. The parasitic weight of the gas tube and the spent gas generator is released thereby keeping the free-fall weight of the corner reflector to a minimum.

The inventors have successfully manufactured a corner reflector in accordance with the invention which has very small packed volume and weight. This allows for the deployment of multiple reflectors from a single decoy round.

Claims

1. A collapsible corner reflector assembly containing multiple collapsible corners, each collapsible corner comprising three reflecting planes disposable mutually at right angles and supported by six stressed struts disposed in two sets of three struts, the two sets of struts being arranged to occupy opposing corners of the fully disposed reflector assembly, the first set of struts being pinned at a common terminus to a piston, the piston being disposed in the bore of a piston tube with the struts aligned substantially in parallel with the axis of the piston tube, a hub having a central aperture through which the first set of struts are arranged to slide in an axial direction on deployment of the piston by means of a propellant device and an external perimeter surface to which the second set of : flexible struts is hingedly attached, the hub being situated at a first end of said piston tube and the propellant device disposed at a ri:.. second end of the piston tube.

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2. A collapsible corner reflector as claimed in claim 1 wherein the propellant device comprises a small volume pyrotechnic gas generator configured on initiation to provide a gaseous release which drives the piston up the piston tube.

3. A collapsible corner reflector as claimed in claim 1 wherein the gas generator is attached to the piston tube by means of a screw thread.

4. A collapsible corner reflector as claimed in any preceding claim a radially extending recess into which the hub is releasably clipped, the recess providing an anchor point for the hub during inflation of the corner reflector.

5. A collapsible corner reflector as claimed in claim 4 wherein deployment of the piston is configured so as to effect release of the hub from the recess once the reflector has been fully deployed allowing parasitic weight of the spent propellant device to be released.

6. A collapsible corner reflector as claimed in any preceding claim wherein the struts are configured to be adjustable in length to accommodate a range of reflector sizes.

7. A collapsible corner reflector assembly substantially as claimed *::::* herein and with reference to the accompanying drawings.

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