Abstract:
The decoy system, notably for terrestrial mines or improvised explosive devices, includes: a means of producing heat energy including an air or water boiler, a means of emitting radiation in the infrared spectrum including a chamber that is fed with fluid by the production means, the chamber being provided with internal fins able to promote a build-up of heat energy inside said chamber, at least one detection means for determining the temperature of the chamber or the temperature of the fluid between the production means and the emission means, and a control unit able to control the operation of the heat energy production means at least according to the determined temperature.

Description:
PRIORITY CLAIM 
     The present application is a continuation of U.S. patent application Ser. No. 12/752,865, filed Apr. 1, 2010, which claims priority to French Patent Application FR 0952203 filed Apr. 3, 2009 which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to the field of decoy systems, notably for mines or explosive devices, laid, buried or more generally arranged at the roadside. More specifically, the invention relates to the decoying of improvised explosive devices which usually contain destructive, flammable and/or deadly chemical products that are commonly called IED (improvised explosive devices). The invention also relates, generally, to the decoy systems or decoys that make it possible to provoke the triggering of explosive devices or mines buried or placed at the roadside. 
     2. Description of the Relevant Art 
     Conventionally, decoy systems or decoys are used to provoke the explosion of mines or explosive devices at a distance from the mine-clearing vehicles. 
     To this end, the decoy systems can comprise means for emitting radiation in the infrared spectrum so as to be detected by these devices or mines that include infrared sensors. 
     To allow for the emission of such radiation, one solution consists in fitting, between two metallic plates, an electrical resistance powered by an energy source. 
     In order to ensure an emission of infrared radiation that is likely to provoke the triggering of both mines and improvised explosive devices, it is, however, necessary for the electrical energy power source to be able to have a relatively high power, of the order of several kilowatts. 
     This is incompatible with an embedded system on-board a vehicle or pushed by a mine-clearing vehicle that also has to be used for several hours. Moreover, with this solution, the temperature rise time of the system is relatively great. 
     In order to provide the infrared radiation emission means with an input of electrical energy that is sufficient to allow for the triggering of mines and improvised explosive devices, it is possible to use a generator set. However, this solution has the major drawbacks of being relatively bulky and very heavy. 
     Also known, from the European Patent 1 054 230, is a decoy system linked to the front of a tank and mainly comprising vertical panels on which are provided metal conductors powered by the electric batteries of the tank to control their temperature. 
     The purpose of this system is to reproduce emissivity in the infrared range close to that of a tank to allow for the triggering of roadside mines. In this respect, one area of the panels can be slaved to a temperature of between 15 and 20° C. above ambient temperature, whereas a neighboring area of the panels can be slaved to a lower temperature, for example between 5 and 10° C. above ambient temperature. 
     Given the heat dissipation, the electrical energy supplied to the panels by the batteries can prove insufficient to allow for the triggering of roadside mines as soon as the tank is moving at relatively high speeds, of the order of 50 kilometers per hour. 
     Moreover, the electrical energy likely to be delivered by the batteries of the tank does not make it possible to obtain a sufficient temperature on the panels to allow for the triggering of improvised explosive devices. In practice, such devices usually explode when they detect a temperature higher than those recommended in EP 1 054 230. 
     SUMMARY OF THE INVENTION 
     The aim of the present embodiments is to remedy the drawbacks of the prior art systems. 
     More particularly, the embodiments herein provide a decoy system, notably for terrestrial improvised explosive devices, that is autonomous, cost-effective and compact. 
     Another aim of the embodiments is to provide a decoy system for which the temperature rise time, when it is started up, is relatively short. 
     A further aim of the embodiments is to provide a system that makes it possible to trigger both mines arranged at the roadside and also improvised explosive devices. 
     In one embodiment, the decoy system, notably for mines or terrestrial improvised explosive devices, is provided with a means of producing heat energy including an air or water boiler and a means of emitting radiation in the infrared spectrum including a chamber fed with fluid by the heat energy production means. The chamber is provided with internal fins able to promote a build-up of heat energy inside the latter. The system also includes at least one detection means for determining the temperature of the chamber or the temperature of the fluid between the production means and the emission means, and a control unit able to control the operation of the means of producing heat energy at least according to the determined temperature. 
     In one embodiment, the system also includes an outside temperature sensor. The control unit is able to drive the production means so that the difference between the detected temperatures is greater than a predetermined threshold value and able to check that said difference is at least equal to said threshold value. 
     Advantageously, the internal fins extend perpendicularly to the inlet stream into the chamber of the fluid emitted by the heat energy production means. The internal fins can be arranged in the form of successive rows, parallel or not, the fins of one row being separated so as to delimit a space located at least partly facing an orifice feeding the chamber with fluid. Advantageously, the dimension of the space provided between the internal fins of a row decreases progressively from one row of fins to another. The space between the fins is greatest for the row located in the vicinity of the feed orifice. 
     In one embodiment, the chamber includes substantially smooth outer walls. 
     Advantageously, the boiler includes an exhaust duct for gases passing through the chamber. 
     The chamber can include at least one fluid outlet orifice and, possibly, an associated closing valve. The position of the closing valve can be modified manually or mechanically via the control unit. 
     In one embodiment, a recirculation duct tapped onto the chamber is provided to reinject, partially or totally inside the boiler, the fluid from the chamber. This duct extends between the chamber and the boiler and is in fluidic communication with them. 
     In one embodiment, the means of detecting the temperature of the chamber includes a temperature sensor. 
     In one embodiment, the control unit is able to control the operation of the energy production means according to the difference between the measured temperatures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood from reading the detailed description of an embodiment taken as a nonlimiting example and illustrated by the appended drawings, in which: 
         FIGS. 1 to 3  diagrammatically represent a decoy system, and 
         FIG. 4  is a perspective cross-sectional view of an infrared radiation emission means of the system of  FIGS. 1 to 3 . 
     
    
    
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but to the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  diagrammatically represents a decoy system  10  mounted on a supporting mast  12 , which is in turn fixed to a towing bar  14  which is attached to the front part of a vehicle  16 . As illustrated in  FIG. 2 , the supporting mast  12  can alternatively be fixed directly to the front of the vehicle  16 . 
     The decoy system  10  is particularly suitable for making it possible, ahead of the passage of the vehicle  16 , to trip a mine or improvised explosive device laid on a road or buried. The distance separating the system  10  and the front of the vehicle  16  is sufficiently great to avoid destruction of the vehicle  16  when the mine or device explodes. 
     As illustrated more visibly in  FIG. 3 , the decoy system  10  mainly includes a boiler  20  for the production of heat energy and an infrared radiation emission means  22  supplied with fluid by the boiler. The boiler  20  and the emission means  22  are fixed by any appropriate means to a supporting shielding  24 . The supporting shielding  24  includes clamping plates  26  and screws (not represented) for adjusting the position of and securing the system  10  on the mast  12  ( FIGS. 1 and 2 ). The emission means  22  is in a vertical position so as to be able to be detected by the sensor associated with the mine or explosive device. 
     The boiler  20  is used to reheat a fluid, in this case air, and direct it to the means  22  for the purpose of the emission of radiations, in the infrared spectrum, likely to provoke the tripping of a mine or improvised explosive device. 
     The boiler  20  is connected to a fuel tank  28  via a duct  30 . The boiler  20  includes a burner, a dosing pump and a ventilation means (not represented). The ventilation means sucks in air from an inlet opening  32  provided at a bottom end of the shielding  24  and expels it toward an exhaust duct  41 , after having mixed it with the fuel pumped from the tank  28  then passed through the burner. The reheated air at the outlet of the boiler  20  is conveyed by a duct  37  to feed the emission means  22 . As an indication, the boiler  20  can have a length of 550 mm, and a width and a thickness of 200 mm. In this embodiment, the boiler is of the air type. Alternatively, it is, however, possible to provide a water boiler to feed the emission means  22  with heat energy. 
     There now follows a description, with reference to  FIG. 4 , of the infrared radiation emission means  22 . The emission means  22  is represented here in cross section, the part of the emission means  22  not illustrated in the figure being identical to that which will be described. 
     The emission means  22  includes a sealed chamber  34  provided internally with fins  36   a ,  36   b  arranged in the form of parallel successive rows, in this case twelve such rows. The chamber  34  is made of light alloy and here has a generally parallelepipedal shape. Obviously, the chamber  34  could have a different overall shape. Alternatively, it could also be possible to provide non-parallel fins. As an indication, the chamber  34  can have a height of 400 mm, a width of 800 mm and a thickness of 110 mm. The system  10  can have a weight of approximately 30 kg. The chamber  34  includes pairs of opposite edges  34   a ,  34   b  and  34   c ,  34   d . In this figure, the emission means  22  is represented in a position that is assumed to be vertical. The edges  34   a ,  34   b  therefore respectively constitute top and bottom edges. The chamber  34  is fed with hot air via the duct  37  which extends from the boiler  20  and is fixedly mounted inside a feed orifice  38  provided in the top edge  34   a.    
     As indicated previously, the horizontal internal fins  36   a ,  36   b  are arranged in the form of parallel successive rows. The vertical spacing provided between two immediately adjacent rows of fins is constant. 
     The fins  36   a ,  36   b  extend between the edges  34   c  and  34   d , being parallel to the edges  34   a  and  34   b . The fins  36   a ,  36   b  of the first row situated in the vicinity of the duct  37  occupy substantially most of the width of the chamber  34  between the edges  34   c ,  34   d . A first fin  36   a  of this row extends from the edge  34   c  to the vicinity of an area situated in the extension of the duct  37 , i.e. facing the feed orifice  38 . The second fin  36   b  extends horizontally in the extension of the first fin  36   a  while being laterally offset relative to the latter until it reaches the vicinity of the edge  34   d , while allowing a small space to remain between it and said edge. The fins  36   a ,  36   b  of the first row are separated from one another so as to delimit a space  40  situated facing the feed orifice  38 . The lateral dimension of the space  40  is substantially equal to the diameter of the feed orifice  38 . The space  40  allows the air inlet flow to be directed to the subsequent rows of fins  36   a ,  36   b.    
     Downstream of the first row, using the direction of circulation of the air inside the chamber  34  as a reference, the second row includes a fin  36   a  extending from the edge  34   c . The fin  36   a  of the second row has a length slightly greater than that of the fin  36   a  of the first row. The fin  36   b  of the second row has a length identical to that of the first row while, however, being offset toward the fin  36   a  of the second row so that the space  40  between fins of that row is slightly less than that of the first row. Thus, a greater space is provided between the fin  36   b  of the second row and the edge  34   d.    
     The arrangement of each of the subsequent rows of fins relative to the immediately preceding row is similar to that of the second row with respect to the first row. Thus, the space  40  between the fins  36   a ,  36   b  of one and the same row gradually decreases with distance away from the feed orifice  38  so that, for the last row of fins  36   a  and  36   b  situated in proximity to the bottom edge  34   b , the space between the two fins is almost zero. The space between the fin  36   b  of this last row and the edge  34   d  is substantially equal to the diameter of an outlet orifice  39  provided in the thickness of the bottom edge  34   b  in the vicinity of the edge  34   d . The applicant has determined that the provision of a space  40  between fins that has a general V shape and decreases with distance away from the feed orifice  38  allows for a better distribution of the heat inside the chamber  34 . Thus, a relatively uniform temperature of the chamber  34  is obtained. 
     The fins  36   a ,  36   b  of the different rows are arranged perpendicularly to the direction of flow of the air at the outlet of the duct  37  so as to retain this air flow within the chamber  34  while progressively orienting it toward the outlet orifice  39 . The arrangement of the internal fins  36   a ,  36   b  in the chamber  34  tends to favor the concentration of heat inside the latter so as to facilitate the emission of an infrared radiation that is substantially greater than the ambient infrared radiation. The appearance of a hot area or spot that can be detected by a mine or improvised explosive device is thus obtained. Obviously, it could be possible to provide a different arrangement of the fins  36   a ,  36   b  also tending to favor the concentration of heat. Furthermore, so as to limit the heat dissipation by the emission means  22 , the outer walls of the chamber  34  are substantially smooth, i.e. without any fins or other means favoring the evacuation of heat. 
     To adjust the hot air flow rate at the outlet from the chamber  34 , the latter includes a valve  42 , the position of which can be modified manually or mechanically, for example as a function of the outside temperature, so as to vary the degree of opening of the outlet orifice  39 . Alternatively, it is possible not to provide such a valve. 
     In a variant embodiment, it is also possible to provide a closed circuit mode of operation of the system. To this end, the chamber  34  includes, instead of the outlet orifice  39  or in association with said orifice and its closing valve  42 , a recirculation duct communicating with the inside of the chamber and reinjecting the hot air, or water, obtained from the chamber inside the boiler. Such a closed circuit mode of operation is possible by virtue of the use of an air or water boiler. 
     The exhaust duct  41  for the gases from the boiler  20  snakes up and down inside the chamber  34 . The exhaust duct  41  extends through the top edge  34   a  in the vicinity of the duct  37  and discharges through the bottom edge  34   b  in proximity to the outlet orifice  39 . The exhaust duct  41  participates in the raising of the temperature of the chamber  34  when the system  10  is started up, thus helping to reduce the time needed for the emission of the desired infrared radiation. 
     Referring once again to  FIG. 3 , the decoy system  10  also includes a control unit  46  fixed to the shielding  24  and controlling the operation of the boiler  20  as a function of the infrared radiation to be emitted. 
     To this end, the system  10  includes a temperature sensor  48  mounted in the duct  37  and able to measure the temperature of the hot air at the outlet of the boiler  20  which is conveyed to the chamber  34 . The system  10  also includes a temperature sensor  50  mounted on the shielding  24  between the inlet opening  32  and the inlet of the boiler  20  so as to measure the temperature of the outside air that is directed toward said boiler. The temperature sensors  48 ,  50  are connected to the control unit  46  via connections  52 ,  54  that are diagrammatically illustrated as dotted lines. 
     The control unit  46  includes, stored in memory, all the hardware and software means that make it possible to control the operation of the boiler  20  on the basis of measurements made by the sensors  48 ,  50 . In this respect, the control unit  46  determines the difference between the temperature of the hot air entering into the chamber  34  and the outside temperature, and compares it to a predetermined threshold value. If the temperature difference is below the threshold value, an alarm signal that can be visual or audible is triggered by the control unit  46  to signal a failure of the operation of the boiler  20 . As a variant, the control unit  46  can drive the operation of the boiler  20  so as to maintain the difference between the temperature of the hot air entering into the chamber  34  and the outside temperature at a fixed value. 
     In the embodiment described, the operation of the boiler is controlled and/or driven on the basis of the temperature measurements of the hot air introduced into the chamber  34  and of the outside air. It will be understood that it is also possible, without departing from the framework of the invention, to provide for the mounting of one or more temperature sensors directly inside the chamber  34  replacing the temperature sensor of the hot air mounted in the duct  37 . In the case of a plurality of temperature sensors mounted in the chamber  34  in different places, it is possible to provide for the control unit  46  to calculate an average of the measured temperatures in order to obtain a value representative of the temperature of the walls of the chamber  34 . 
     In a variant embodiment, it is also possible to determine the temperature of the chamber  34  by means of charts or maps stored in the control unit  46  and obtained from previous trials on the basis of temperature measurements on the hot air introduced inside the latter, of the temperature of the outside air, and of the speed of the vehicle  16  to which the system  10  is attached. 
     Alternatively, it is also possible to provide for the control unit  46  to drive the operation of the boiler  20 , and therefore that of the emission means  22 , only as a function of the temperature of the chamber  34  determined by the sensor or sensors, i.e., without considering the temperature of the outside air. 
     In the embodiments described, the sensor or sensors provided for measuring the temperature of the hot air in the duct  37  or in the chamber  34  are temperature sensors. Alternatively, to measure the temperature of the chamber  34  or of the air inside the duct  37 , it could be possible to provide a thermal analysis infrared sensor able to detect the infrared radiation emitted and convert it into an electrical signal in order for the control unit  46  to determine the temperature of the chamber  34  or of the air inside the duct  37 . 
     When the system  10  is intended for use at altitude, for example above 1500 meters, it is possible to provide, in addition, an atmospheric pressure sensor (not represented) mounted on the shielding  24  and directly connected to the boiler so as to be able to regulate its combustion according to the density of the air to be burned, which reduces with altitude. 
     The means  22  makes it possible to obtain, continuously, at the level of the chamber  34 , a temperature substantially greater than that which can be obtained with other technologies with comparable supplied energy, which makes it possible to generate a significant temperature difference with the outside temperature so as to be able to be detected equally by a mine arranged at the roadside and by an improvised explosive device, and to do so even when the speed of displacement of the vehicle  16  is relatively high, of the order of 50 kilometers per hour. Furthermore, with the system  10 , a relatively short temperature rise time of the chamber  34  is obtained and the system can operate autonomously for several tens of hours at a stretch. It is, moreover, relatively compact and lightweight. 
     In the application described, the system  10  is pushed by a following vehicle  16 . It will easily be understood that this vehicle  16  can be a transport vehicle or else a remotely-operated vehicle. As indicated previously, the system  10  is particularly suitable for the decoying of mines or improvised explosive devices. The system can, however, be used for other applications, for example for decoying infrared airborne missiles. 
     Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.