INFRARED SHIELD

Abstract: An infrared shield for vehicles which have heat radiating areas, in which the shield (7) is formed of a material of low heat transmission characteristics, and is attached to extend over the area to be shielded and is flexible and is arranged to project at least in part form its attachment means (4) and optionally forms fronds (1) to allow movement of at least part of the shield to increase convective and radiative cooling. An intermediate rigid heat insulating shield may be interposed between the shield and the hot area.

Description: "INFRARED SHIELD" This invention relates to an Infrared Shield and in particular it relates to a shield for use on vehicles where heat sources exist which render the vehicles susceptible to location by infrared surveillance devices and attack by infrared homing missiles or the like. A special application of the invention is to tanks and other fighting vehicles where there are considerable heat sources and in which, for instance, parts- of the body, the wheels and tracks, reach temperatures sufficiently high to be located by infrared cameras and infrared surveillance devices, or to attract infrared homing missiles. It is the object of the present invention to provide a form of protection against the detection by means of their infrared sources of the whereabouts of tanks or other vehicles and also at the same time to provide a protection against attack by heat-seeking missiles, a further object being to provide this protection in the form of a simple and effective arrangement which can be applied to tanks or other vehicles and which will be rugged and. durable when moving through the difficult terrain conditions in which tanks and similar vehicles often operate. It is also an object to provide a form of protection which does not add materially to the weight of the vehicle and which will generally decrease the detection of Che vehicles by any other presently known detection method based on electro¬ magnetic radiation. OMPI Generally th invention consists in the use of a material which mimics the thermal characteristics of leaves and bushes, or the general terrain in which the vehicle operates, and shades the vehicle from solar radiation and provides much-increased surface- area for convective and radiative cooling. This can conveniently be achieved by using a material of low heat transmission characteristics to act as a heat shield, a suitable material being canvas, and which material can be attached to the vehicle to preferably flap or waft in any breeze to aid in convective cooling. Such a heat shield may be cut from a length of canvas or a similar material and is provided with support means at least along one edge, the material projecting from the support means to be clear of contact with the heat source and preferably cut to form fronds. In the case of a vehicle the attachment means run generally in the direction of travel of the vehicle, that is in the case of a tank or vehicle, in a horizontal direction. The invention comprises an infrared shield for objects such as vehicles which have heat radiating areas and which shield is adapted to be secured to the object to be interposed between the heat radiating area and infrared surveillance devices or infrared guided missiles, characterised in that the shield is formed of a material having thermal characteristics similar to those of bushes and leaves and is flexible and arranged to project from its attachment means whereby to allow movement of at least part of the material to increase convective and radiative cooling. The material maybe canvas and is slitted to form fronds projecting freely from the attachment means. In order however that the invention may be more fully understood, embodiments thereof will now be described with reference to the accompanying drawings in which: FIG. 1 is a front view of a form of the invention using fronds, FIG. 2 is an end view thereof, FIG. 3 is a view similar to FIG. 1 but showing how the fronds move under wind or other displacing force, FIG. 4 is a side elevation of an armoured personnel carrier fitted with a form of the invention, FIG. 5 is a front view thereof FIG. 6 is a rear view thereof, and FIG. 7 is an enlarged fragmentary section on line A of FIG. 4. Referring first to FIGS. 1, 2 and 3, the fronds 1 are shaped from a material such as canvas and are formed by providing a series of slits 2 in the material but having an attachment portion 3 which is folded over to form a loop 4 through which a support member such as a wire 5 can be passed, the loop being closed by stitching 6. As will be seen from FIG. 3, the fronds 1 depend from the wire support member 5 so that they can be brushed back by bushes or the like through which the tank or vehicle operates without being torn off, and we have found that if these fronds are twisted and are stiff enough so as not to lie flat against the panels they provide a high degree of heat isolation to the parts covered by them which would otherwise increase their temperatures owing to solar heating and release sufficient heat to be detected by infrared surveillance devices, or to be attacked by missiles arranged to home on a heat source. These shields are generally designated 7. The invention can be applied in association with other protective heat shields, and can for instance be mounted to protect hub caps, the wheels and the tracks of such vehicles, as shown in FIGS. and 7, and In the case of wheel protection can be in the form of a series of layered canvas rings 8 held in place by a rigid disc 9 which is secured to the wheel 10 to extend over the centre part of the wheel and by a second rigid member 11, the said rigid members 9 and 11 being separated by an interposed pad 12 of insulating material which limits transfer of heat from road wheels or the like to the rigid member 9. The hot outer metal surfaces of the vehicle can be covered by wood or insulating materials. The assembly of FIG. 7 can readily be applied to wheeled or track vehicles whether pneumatic, solid rubber or- of metal, the rings 8 being flexible to accommodate to required displacement. Insulating panels similar to that described and shown in FIG. 7 (upper part) can be positioned over any hot areas of the body, and may cover the major portion of a body in cases where heating of the body is by friction, heat generation or heat trans¬ missions from the engine or exhaust or the like. Referring to FIGS. 4, 5 and 6, the vehicle body has a series of horizontal wires 5 stretched hori¬ zontally along the sides of the body 15 as shown in the area 16, but on these- wires 5, as shown in the areas 17, are positioned a multiplicity of the shields 7 having the fronds 1 spaced to cover the body 15. These shields can simply cover the body 15 but are spaced slightly therefrom to allow freedom of movement under wind or when brushing against foliage or the like. In the area designated 19 the shields are placed over- a support comprising pairs of metal members as shown in FIG. 7 with an interposed pad of insulating material, such as. urethane foam, and the shields 7 are attached on wires extending over this area. The area 20 may be similarly protected. In the case of the front and back skirts 22 and 23, these are of canvas or the like slitted OMPI VIPO along the lower part to form fronds and attached at the top by attachment members 24. The track flaps 25 can be similarly constructed but need not be slitted. It has been found that it is advantageous to colour the material similar to the leaves or background through which the tank or vehicle moves and to choose the material to ensure that it has the same thermal and radiation characteristics as the bushes and the general terrain so that then the possibility of detection of a tank or other vehicle is greatly reduced as the hot spots on the vehicle are protected by the fronds or other heat shielding members of canvas or the like. Using fronds which are sufficiently strong to be twisted, yet stiff enough so as not to lie flat against the panels or the part being protected is hightly advantageous, and if the material is chosen to have a similar thermal conductivity and a similar thermal inertia and reflectivity and emission as leaves or bushes of the terrain in which the vehicle operates a great advance in safety results because of the difficulty of then detecting any hot spots in the vehicle which would otherwise make it susceptible to acquisition by infrared surveillance devices or attack by heat-seeking missiles. While the invention is generally adapted to work in wavelengths from 3 to 14 micrometres, it also provides protection in other wavebands. OMPI

Claims: AMENDED CLAIMS [received by the International Bureau on 13 December 1983 (13.12.83); original claims 1 and 7 have been amended, original claims 2-6 and 8—12 unchanged] 1. An infrared shield for objects such as vehicles which have heat radiating areas and which is adapted to be secured to the object so as to be Interposed between the heat radiating area and heat sensitive surveillance devices or heat-seeking missiles, and also to be between the sun and the surfaces of the vehicle to shade those surfaces to prevent them from rising in temperature above the temperature of the natural background owing to solar heating, characterised in that the said shield is formed of a material of low heat transmission character¬ istics, has attachment means, has a substantially continuous surface and is arranged to have portions project from its attachment means whereby to allow movement of at least part of the said shield to increase convective and radiative cooling. 2. An infrared shield according to claim 1 wherein at least the projecting portions of the said shield are slitted to form a series of fronds projecting from the attachment means. 3. An infrared shield according to claim 1 wherein the said shield has an attachment portion along one edge but wherein the said shield is slitted outwards from the said attachment portion to form a series of parallel fronds projecting outwards from the said attachment means. 4. An infrared shield according to claim 1, 2 or 3 wherein the said shield is formed of at least one layer of canv s. 5. An infrared shield according to claim 1 wherein the said shield is associated with a first rigid member of low heat transmission characteristics which is adapted to be fitted to the said object over a said heat radiating- area, and has supported on it to project beyond the said rigid member a second flexible member having at least its surface continuous and of a low heat transmission character¬ istic. 6. An infrared shield according to claim 5 characterised in that the said second flexible member is formed of at least one layer of canvas. 7. An. infrared shield according to claim 6 wherein the said projecting portion is slitted to form fronds projecting outwards from the said first rigid member. 8. An infrared member according to claim 5, 6 or 7 wherein the said first rigid member is formed of two rigid members spaced apart by a layer of urethane foam. 9. An infrared shield according to claim 2 wherein the said shield is positioned over a rigid shield comprising a pair of rigid members spaced apart by a layer of urethane foam. 10. An infrared shield according to claim 2 or 3 wherein the said fronds are twisted. \l 11. An infrared shield according to claim 2 wherein the said shield has a thermal conductivity and a similar thermal inertia and emission as leaves or bushes. 12. An infrared shield constructed substantially as described with reference to either of FIGS. 1, 2 and 3, or FIG. 4 or FIG. 5 or FIG. 6 or FIG. 7.

Inventors: CONSIDINE JOHN, SCOTT OWEN SEYMOUR, CONSIDINE, JOHN, SCOTT, OWEN, SEYMOUR
Applicants: COMMW OF AUSTRALIA, THE COMMONWEALTH OF AUSTRALIA, CARE OF THE SECRETA
Application year: 1983
Main classification: F41H3
IPC codes: B63G13, D06N7, F16L59, F41H3, G12B17